diff --git a/INSTALL b/INSTALL
index 5a82044597..729de8d20f 100644
--- a/INSTALL
+++ b/INSTALL
@@ -132,7 +132,7 @@ mock 1.0.1 (http://pypi.python.org/pypi/mock/)
 nose 1.1.2 or later (https://nose.readthedocs.io/en/latest/)
     Python package for software testing. Iris is not compatible with nose2.
 
-pep8 1.4.6* (https://pypi.python.org/pypi/pep8) 
+pep8 1.4.6 (https://pypi.python.org/pypi/pep8)
     Python package for software testing.
 
 pandas 0.11.0 or later (http://pandas.pydata.org)
diff --git a/conda-requirements.txt b/conda-requirements.txt
index f533a424dc..ade5ffd137 100644
--- a/conda-requirements.txt
+++ b/conda-requirements.txt
@@ -17,7 +17,7 @@ setuptools
 # Iris testing/documentation dependencies
 mock
 nose
-pep8=1.5.7
+pep8
 sphinx
 iris_sample_data
 filelock
diff --git a/lib/iris/_concatenate.py b/lib/iris/_concatenate.py
index 768ddf54c0..2da88f39d4 100644
--- a/lib/iris/_concatenate.py
+++ b/lib/iris/_concatenate.py
@@ -341,12 +341,13 @@ def __init__(self, cube):
         # Collate the auxiliary coordinate metadata and scalar coordinates.
         #
         axes = dict(T=0, Z=1, Y=2, X=3)
+
         # Coordinate sort function - by guessed coordinate axis, then
         # by coordinate definition, then by dimensions, in ascending order.
-        key_func = lambda coord: (axes.get(guess_coord_axis(coord),
-                                           len(axes) + 1),
-                                  coord._as_defn(),
-                                  cube.coord_dims(coord))
+        def key_func(coord):
+            return (axes.get(guess_coord_axis(coord), len(axes) + 1),
+                    coord._as_defn(),
+                    cube.coord_dims(coord))
 
         for coord in sorted(cube.aux_coords, key=key_func):
             dims = cube.coord_dims(coord)
@@ -647,8 +648,7 @@ def concatenate(self):
 
             # Sequence the skeleton segments into the correct order
             # pending concatenation.
-            key_func = lambda skeleton: skeleton.signature.dim_extents
-            skeletons.sort(key=key_func,
+            skeletons.sort(key=lambda skeleton: skeleton.signature.dim_extents,
                            reverse=(order == _DECREASING))
 
             # Concatenate the new dimension coordinate.
diff --git a/lib/iris/_constraints.py b/lib/iris/_constraints.py
index 9e3ee2426f..eb255f328b 100644
--- a/lib/iris/_constraints.py
+++ b/lib/iris/_constraints.py
@@ -264,11 +264,15 @@ def extract(self, cube):
             desired_values = list(self._coord_thing)
             # A dramatic speedup can be had if we don't have bounds.
             if coord.has_bounds():
-                call_func = lambda cell: cell in desired_values
+                def call_func(cell):
+                    return cell in desired_values
             else:
-                call_func = lambda cell: cell.point in desired_values
+                def call_func(cell):
+                    return cell.point in desired_values
         else:
-            call_func = lambda c: c == self._coord_thing
+            def call_func(c):
+                return c == self._coord_thing
+
             try_quick = (isinstance(coord, iris.coords.DimCoord) and
                          not isinstance(self._coord_thing, iris.coords.Cell))
 
diff --git a/lib/iris/analysis/__init__.py b/lib/iris/analysis/__init__.py
index 46618abf16..8bc74d37ba 100644
--- a/lib/iris/analysis/__init__.py
+++ b/lib/iris/analysis/__init__.py
@@ -283,39 +283,50 @@ def coord_comparison(*cubes):
 
         # Get all coordinate groups which aren't complete (i.e. there is a
         # None in the group)
-        coord_is_None_fn = lambda cube, coord: coord is None
+        def coord_is_None_fn(cube, coord):
+            return coord is None
+
         if coord_group.matches_any(coord_is_None_fn):
             ungroupable.add(coord_group)
 
         # Get all coordinate groups which don't all equal one another
         # (None -> group not all equal)
-        not_equal_fn = lambda cube, coord: coord != first_coord
+        def not_equal_fn(cube, coord):
+            return coord != first_coord
+
         if coord_group.matches_any(not_equal_fn):
             not_equal.add(coord_group)
 
         # Get all coordinate groups which don't all share the same shape
         # (None -> group has different shapes)
-        diff_shape_fn = lambda cube, coord: coord.shape != first_coord.shape
+        def diff_shape_fn(cube, coord):
+            return coord.shape != first_coord.shape
+
         if coord_group.matches_any(diff_shape_fn):
             different_shaped_coords.add(coord_group)
 
         # Get all coordinate groups which don't all share the same data
         # dimension on their respective cubes
         # (None -> group describes a different dimension)
-        diff_data_dim_fn = lambda cube, coord: \
-            cube.coord_dims(coord) != first_cube.coord_dims(first_coord)
+        def diff_data_dim_fn(cube, coord):
+            return cube.coord_dims(coord) != first_cube.coord_dims(first_coord)
+
         if coord_group.matches_any(diff_data_dim_fn):
             different_data_dimension.add(coord_group)
 
         # get all coordinate groups which don't describe a dimension
         # (None -> doesn't describe a dimension)
-        no_data_dim_fn = lambda cube, coord: cube.coord_dims(coord) == ()
+        def no_data_dim_fn(cube, coord):
+            return cube.coord_dims(coord) == ()
+
         if coord_group.matches_all(no_data_dim_fn):
             no_data_dimension.add(coord_group)
 
         # get all coordinate groups which don't describe a dimension
         # (None -> not a scalar coordinate)
-        no_data_dim_fn = lambda cube, coord: coord.shape == (1, )
+        def no_data_dim_fn(cube, coord):
+            return coord.shape == (1, )
+
         if coord_group.matches_all(no_data_dim_fn):
             scalar_coords.add(coord_group)
 
diff --git a/lib/iris/analysis/_interpolation.py b/lib/iris/analysis/_interpolation.py
index d9ab6e6846..6266f8be6d 100644
--- a/lib/iris/analysis/_interpolation.py
+++ b/lib/iris/analysis/_interpolation.py
@@ -405,8 +405,8 @@ def _setup(self):
                 # Only DimCoords can be circular.
                 if circular:
                     coord_points = extend_circular_coord(coord, coord_points)
-                offset = ((coord_points.max() + coord_points.min() - modulus)
-                          * 0.5)
+                offset = 0.5 * (coord_points.max() + coord_points.min() -
+                                modulus)
                 self._circulars.append((circular, modulus,
                                         index, coord_dims[0],
                                         offset))
@@ -634,8 +634,8 @@ def construct_new_coord(coord):
             return new_coord, dims
 
         def gen_new_cube():
-            if (isinstance(new_coord, DimCoord) and len(dims) > 0
-                    and dims[0] not in dims_with_dim_coords):
+            if (isinstance(new_coord, DimCoord) and len(dims) > 0 and
+                    dims[0] not in dims_with_dim_coords):
                 new_cube._add_unique_dim_coord(new_coord, dims)
                 dims_with_dim_coords.append(dims[0])
             else:
diff --git a/lib/iris/coord_categorisation.py b/lib/iris/coord_categorisation.py
index 189177946a..0c6aadd3f7 100644
--- a/lib/iris/coord_categorisation.py
+++ b/lib/iris/coord_categorisation.py
@@ -81,8 +81,10 @@ def add_categorised_coord(cube, name, from_coord, category_function,
         str_vectorised_fn = np.vectorize(category_function, otypes=[object])
         # Use a common type for string arrays (N.B. limited to 64 chars)
         all_cases_string_type = '|S64' if six.PY2 else '|U64'
-        vectorised_fn = lambda *args: str_vectorised_fn(*args).astype(
-            all_cases_string_type)
+
+        def vectorised_fn(*args):
+            return str_vectorised_fn(*args).astype(all_cases_string_type)
+
     else:
         vectorised_fn = np.vectorize(category_function)
     new_coord = iris.coords.AuxCoord(vectorised_fn(from_coord,
diff --git a/lib/iris/coord_systems.py b/lib/iris/coord_systems.py
index 66a93c5ad5..1d23225940 100644
--- a/lib/iris/coord_systems.py
+++ b/lib/iris/coord_systems.py
@@ -911,9 +911,9 @@ def __init__(self, latitude_of_projection_origin=0.0,
         self.ellipsoid = ellipsoid
 
     def __repr__(self):
-        return "LambertAzimuthalEqualArea(latitude_of_projection_origin={!r}, "\
-               "longitude_of_projection_origin={!r}, false_easting={!r}, "\
-               "false_northing={!r}, ellipsoid={!r})".format(
+        return ("LambertAzimuthalEqualArea(latitude_of_projection_origin={!r},"
+                " longitude_of_projection_origin={!r}, false_easting={!r},"
+                " false_northing={!r}, ellipsoid={!r})").format(
                    self.latitude_of_projection_origin,
                    self.longitude_of_projection_origin,
                    self.false_easting,
diff --git a/lib/iris/coords.py b/lib/iris/coords.py
index 8a75550992..20d4058b6a 100644
--- a/lib/iris/coords.py
+++ b/lib/iris/coords.py
@@ -964,7 +964,8 @@ def collapsed(self, dims_to_collapse=None):
         if np.issubdtype(self.dtype, np.str):
             # Collapse the coordinate by serializing the points and
             # bounds as strings.
-            serialize = lambda x: '|'.join([str(i) for i in x.flatten()])
+            def serialize(x):
+                return '|'.join([str(i) for i in x.flatten()])
             bounds = None
             string_type_fmt = 'S{}' if six.PY2 else 'U{}'
             if self.bounds is not None:
diff --git a/lib/iris/cube.py b/lib/iris/cube.py
index 3ac2546362..aa234ea71d 100644
--- a/lib/iris/cube.py
+++ b/lib/iris/cube.py
@@ -600,8 +600,8 @@ def _is_single_item(testee):
     We count string types as 'single', also.
 
     """
-    return (isinstance(testee, six.string_types)
-            or not isinstance(testee, collections.Iterable))
+    return (isinstance(testee, six.string_types) or
+            not isinstance(testee, collections.Iterable))
 
 
 class Cube(CFVariableMixin):
@@ -1132,7 +1132,8 @@ def coord_dims(self, coord):
         # Search derived aux coords
         target_defn = coord._as_defn()
         if not matches:
-            match = lambda factory: factory._as_defn() == target_defn
+            def match(factory):
+                return factory._as_defn() == target_defn
             factories = filter(match, self._aux_factories)
             matches = [factory.derived_dims(self.coord_dims) for factory in
                        factories]
@@ -1341,9 +1342,11 @@ def coords(self, name_or_coord=None, standard_name=None,
                 msg = 'The attributes keyword was expecting a dictionary ' \
                       'type, but got a %s instead.' % type(attributes)
                 raise ValueError(msg)
-            attr_filter = lambda coord_: all(k in coord_.attributes and
-                                             coord_.attributes[k] == v for
-                                             k, v in six.iteritems(attributes))
+
+            def attr_filter(coord_):
+                return all(k in coord_.attributes and coord_.attributes[k] == v
+                           for k, v in six.iteritems(attributes))
+
             coords_and_factories = [coord_ for coord_ in coords_and_factories
                                     if attr_filter(coord_)]
 
@@ -2157,13 +2160,16 @@ def __getitem__(self, keys):
         # multiple times)
         dimension_mapping, slice_gen = iris.util.column_slices_generator(
             full_slice, len(self.shape))
-        new_coord_dims = lambda coord_: [dimension_mapping[d] for d in
-                                         self.coord_dims(coord_) if
-                                         dimension_mapping[d] is not None]
 
-        new_cell_measure_dims = lambda cm_: [dimension_mapping[d] for d in
-                                             self.cell_measure_dims(cm_) if
-                                             dimension_mapping[d] is not None]
+        def new_coord_dims(coord_):
+            return [dimension_mapping[d]
+                    for d in self.coord_dims(coord_)
+                    if dimension_mapping[d] is not None]
+
+        def new_cell_measure_dims(cm_):
+            return [dimension_mapping[d]
+                    for d in self.cell_measure_dims(cm_)
+                    if dimension_mapping[d] is not None]
 
         try:
             first_slice = next(slice_gen)
@@ -2648,9 +2654,9 @@ def _as_list_of_coords(self, names_or_coords):
                 coords.append(self.coord(name_or_coord))
             else:
                 # Don't know how to handle this type
-                msg = "Don't know how to handle coordinate of type %s. " \
-                      "Ensure all coordinates are of type six.string_types or " \
-                      "iris.coords.Coord." % type(name_or_coord)
+                msg = ("Don't know how to handle coordinate of type %s. "
+                       "Ensure all coordinates are of type six.string_types "
+                       "or iris.coords.Coord.") % (type(name_or_coord), )
                 raise TypeError(msg)
         return coords
 
@@ -3316,8 +3322,8 @@ def collapsed(self, coords, aggregator, **kwargs):
             data_result = unrolled_data
 
         # Perform the aggregation in lazy form if possible.
-        elif (aggregator.lazy_func is not None
-                and len(dims_to_collapse) == 1 and self.has_lazy_data()):
+        elif (aggregator.lazy_func is not None and
+                len(dims_to_collapse) == 1 and self.has_lazy_data()):
             # Use a lazy operation separately defined by the aggregator, based
             # on the cube lazy array.
             # NOTE: do not reform the data in this case, as 'lazy_aggregate'
diff --git a/lib/iris/experimental/equalise_cubes.py b/lib/iris/experimental/equalise_cubes.py
index bf3379db66..8a85cded97 100644
--- a/lib/iris/experimental/equalise_cubes.py
+++ b/lib/iris/experimental/equalise_cubes.py
@@ -1,4 +1,4 @@
-# (C) British Crown Copyright 2013 - 2015, Met Office
+# (C) British Crown Copyright 2013 - 2016, Met Office
 #
 # This file is part of Iris.
 #
@@ -45,8 +45,8 @@ def equalise_attributes(cubes):
         cube_keys = list(cube.attributes.keys())
         common_keys = [
             key for key in common_keys
-            if key in cube_keys
-            and np.all(cube.attributes[key] == cubes[0].attributes[key])]
+            if (key in cube_keys and
+                np.all(cube.attributes[key] == cubes[0].attributes[key]))]
 
     # Remove all the other attributes.
     for cube in cubes:
diff --git a/lib/iris/experimental/fieldsfile.py b/lib/iris/experimental/fieldsfile.py
index f8cefe0669..9489277d1f 100644
--- a/lib/iris/experimental/fieldsfile.py
+++ b/lib/iris/experimental/fieldsfile.py
@@ -159,7 +159,8 @@ def adjust(dims):
 
 def _bind_coords(coords_and_dims, dim_coord_dims, dim_coords_and_dims,
                  aux_coords_and_dims):
-    key_func = lambda item: _HINTS.get(item[0].name(), len(_HINTS))
+    def key_func(item):
+        return _HINTS.get(item[0].name(), len(_HINTS))
     # Target the first DimCoord for a dimension at dim_coords,
     # and target everything else at aux_coords.
     for coord, dims in sorted(coords_and_dims, key=key_func):
diff --git a/lib/iris/fileformats/grib/_load_convert.py b/lib/iris/fileformats/grib/_load_convert.py
index 1061d62da8..54a3cbcd38 100644
--- a/lib/iris/fileformats/grib/_load_convert.py
+++ b/lib/iris/fileformats/grib/_load_convert.py
@@ -152,7 +152,9 @@ def unscale(value, factor):
         is returned.
 
     """
-    _unscale = lambda v, f: v / 10.0 ** f
+    def _unscale(v, f):
+        return v / 10.0 ** f
+
     if isinstance(value, Iterable) or isinstance(factor, Iterable):
         def _masker(item):
             result = ma.masked_equal(item, _MDI)
@@ -1072,15 +1074,15 @@ def grid_definition_template_90(section, metadata):
         raise TranslationError('Unsupported space-view orientation.')
 
     # Determine the coordinate system.
-    sub_satellite_lat = (section['latitudeOfSubSatellitePoint']
-                         * _GRID_ACCURACY_IN_DEGREES)
+    sub_satellite_lat = (section['latitudeOfSubSatellitePoint'] *
+                         _GRID_ACCURACY_IN_DEGREES)
     # The subsequent calculations to determine the apparent Earth
     # diameters rely on the satellite being over the equator.
     if sub_satellite_lat != 0:
         raise TranslationError('Unsupported non-zero latitude for '
                                'space-view perspective.')
-    sub_satellite_lon = (section['longitudeOfSubSatellitePoint']
-                         * _GRID_ACCURACY_IN_DEGREES)
+    sub_satellite_lon = (section['longitudeOfSubSatellitePoint'] *
+                         _GRID_ACCURACY_IN_DEGREES)
     major, minor, radius = ellipsoid_geometry(section)
     geog_cs = ellipsoid(section['shapeOfTheEarth'], major, minor, radius)
     height_above_centre = geog_cs.semi_major_axis * section['Nr'] / 1e6
diff --git a/lib/iris/fileformats/netcdf.py b/lib/iris/fileformats/netcdf.py
index 8e3d644633..f67d70bd61 100644
--- a/lib/iris/fileformats/netcdf.py
+++ b/lib/iris/fileformats/netcdf.py
@@ -525,7 +525,9 @@ def _load_cube(engine, cf, cf_var, filename):
     # Populate coordinate attributes with the untouched attributes from the
     # associated CF-netCDF variable.
     coordinates = engine.provides.get('coordinates', [])
-    attribute_predicate = lambda item: item[0] not in _CF_ATTRS
+
+    def attribute_predicate(item):
+        return item[0] not in _CF_ATTRS
 
     for coord, cf_var_name in coordinates:
         tmpvar = filter(attribute_predicate,
@@ -1836,9 +1838,9 @@ def _create_cf_data_variable(self, cube, dimension_names, local_keys=None,
             cf_name = self._increment_name(cf_name)
 
         # if netcdf3 avoid streaming due to dtype handling
-        if (not cube.has_lazy_data()
-                or self._dataset.file_format in ('NETCDF3_CLASSIC',
-                                                 'NETCDF3_64BIT')):
+        if (not cube.has_lazy_data() or
+                self._dataset.file_format in ('NETCDF3_CLASSIC',
+                                              'NETCDF3_64BIT')):
             # Determine whether there is a cube MDI value.
             fill_value = None
             if isinstance(cube.data, ma.core.MaskedArray):
diff --git a/lib/iris/fileformats/nimrod_load_rules.py b/lib/iris/fileformats/nimrod_load_rules.py
index a5dc2922f0..66af00e8a5 100644
--- a/lib/iris/fileformats/nimrod_load_rules.py
+++ b/lib/iris/fileformats/nimrod_load_rules.py
@@ -1,4 +1,4 @@
-# (C) British Crown Copyright 2010 - 2015, Met Office
+# (C) British Crown Copyright 2010 - 2016, Met Office
 #
 # This file is part of Iris.
 #
@@ -156,10 +156,10 @@ def british_national_grid_y(cube, field):
 
     """
     if field.origin_corner == 0:  # top left
-        y_coord = DimCoord(np.arange(field.num_rows)[::-1] *
-                           -field.row_step + field.y_origin,
-                           standard_name="projection_y_coordinate", units="m",
-                           coord_system=iris.coord_systems.OSGB())
+        y_coord = DimCoord(
+            np.arange(field.num_rows)[::-1] * -field.row_step + field.y_origin,
+            standard_name="projection_y_coordinate", units="m",
+            coord_system=iris.coord_systems.OSGB())
         cube.add_dim_coord(y_coord, 0)
     else:
         raise TranslationError("Corner {0} not yet implemented".
diff --git a/lib/iris/fileformats/pp.py b/lib/iris/fileformats/pp.py
index 26a00ab2f5..c5aeb75863 100644
--- a/lib/iris/fileformats/pp.py
+++ b/lib/iris/fileformats/pp.py
@@ -1411,8 +1411,8 @@ def save(self, file_handle):
                     header_elem = int(header_elem)
                 lb[index] = header_elem
             else:
-                index = slice(pos[0] - NUM_LONG_HEADERS, pos[-1]
-                              - NUM_LONG_HEADERS + 1)
+                index = slice(pos[0] - NUM_LONG_HEADERS,
+                              pos[-1] - NUM_LONG_HEADERS + 1)
                 b[index] = header_elem
 
         # Although all of the elements are now populated, we still need to
diff --git a/lib/iris/fileformats/um/_fast_load_structured_fields.py b/lib/iris/fileformats/um/_fast_load_structured_fields.py
index 2ca79bcd6e..214931885f 100644
--- a/lib/iris/fileformats/um/_fast_load_structured_fields.py
+++ b/lib/iris/fileformats/um/_fast_load_structured_fields.py
@@ -120,10 +120,13 @@ def _field_vector_element_arrays(self):
         """Define the field components used in the structure analysis."""
         # Define functions to make t1 and t2 values as date-time tuples.
         # These depend on header version (PPField2 has no seconds values).
-        t1_fn = lambda fld: (fld.lbyr, fld.lbmon, fld.lbdat,
-                             fld.lbhr, fld.lbmin, getattr(fld, 'lbsec', 0))
-        t2_fn = lambda fld: (fld.lbyrd, fld.lbmond, fld.lbdatd,
-                             fld.lbhrd, fld.lbmind, getattr(fld, 'lbsecd', 0))
+        def t1_fn(fld):
+            return (fld.lbyr, fld.lbmon, fld.lbdat, fld.lbhr, fld.lbmin,
+                    getattr(fld, 'lbsec', 0))
+
+        def t2_fn(fld):
+            return (fld.lbyrd, fld.lbmond, fld.lbdatd, fld.lbhrd, fld.lbmind,
+                    getattr(fld, 'lbsecd', 0))
 
         # Return a list of (name, array) for the vectorizable elements.
         component_arrays = [
diff --git a/lib/iris/plot.py b/lib/iris/plot.py
index 9aaba2eb7e..025e32ac42 100644
--- a/lib/iris/plot.py
+++ b/lib/iris/plot.py
@@ -167,8 +167,7 @@ def guess_axis(coord):
             aux_coords = [coord for coord in aux_coords
                           if isinstance(coord, iris.coords.DimCoord)]
             if aux_coords:
-                key_func = lambda coord: coord._as_defn()
-                aux_coords.sort(key=key_func)
+                aux_coords.sort(key=lambda coord: coord._as_defn())
                 coords[dim] = aux_coords[0]
 
     if mode == iris.coords.POINT_MODE:
@@ -974,7 +973,9 @@ def points(cube, *args, **kwargs):
     keyword arguments.
 
     """
-    _scatter_args = lambda u, v, data, *args, **kwargs: ((u, v) + args, kwargs)
+    def _scatter_args(u, v, data, *args, **kwargs):
+        return ((u, v) + args, kwargs)
+
     return _draw_2d_from_points('scatter', _scatter_args, cube,
                                 *args, **kwargs)
 
diff --git a/lib/iris/tests/test_coding_standards.py b/lib/iris/tests/test_coding_standards.py
index ec0c19aba5..c092aa285d 100644
--- a/lib/iris/tests/test_coding_standards.py
+++ b/lib/iris/tests/test_coding_standards.py
@@ -69,6 +69,13 @@
              in exclusion]
 
 
+# pycodestyle / pep8 error codes that should be ignored:
+PYCODESTYLE_IGNORE_OPTIONS = (
+    # "Module level import not at top of file" - due to conditional imports
+    'E402',
+)
+
+
 class StandardReportWithExclusions(pep8.StandardReport):
     expected_bad_files = [
         '*/iris/std_names.py',
@@ -180,6 +187,7 @@ def test_pep8_conformance(self):
         # "reporter=pep8.FileReport" to the StyleGuide constructor.
         pep8style = pep8.StyleGuide(quiet=False,
                                     reporter=StandardReportWithExclusions)
+        pep8style.options.ignore += PYCODESTYLE_IGNORE_OPTIONS
 
         # Allow users to add their own exclude list.
         extra_exclude_file = os.path.join(os.path.dirname(__file__),
diff --git a/lib/iris/tests/test_grib_load_translations.py b/lib/iris/tests/test_grib_load_translations.py
index f33f3078df..f868d8d70d 100644
--- a/lib/iris/tests/test_grib_load_translations.py
+++ b/lib/iris/tests/test_grib_load_translations.py
@@ -252,10 +252,8 @@ def _run_timetests(self, test_set):
                 )
 
                 # Check the data-starttime calculation.
-                interval_start_to_end = (
-                    wrapped_msg._phenomenonDateTime
-                    - wrapped_msg._referenceDateTime
-                )
+                interval_start_to_end = (wrapped_msg._phenomenonDateTime -
+                                         wrapped_msg._referenceDateTime)
                 if grib_edition == 1:
                     interval_from_units = wrapped_msg.P1
                 else:
diff --git a/lib/iris/tests/unit/analysis/cartography/test_rotate_winds.py b/lib/iris/tests/unit/analysis/cartography/test_rotate_winds.py
index 617d919293..19ae497e48 100644
--- a/lib/iris/tests/unit/analysis/cartography/test_rotate_winds.py
+++ b/lib/iris/tests/unit/analysis/cartography/test_rotate_winds.py
@@ -1,4 +1,4 @@
-# (C) British Crown Copyright 2015, Met Office
+# (C) British Crown Copyright 2015 - 2016, Met Office
 #
 # This file is part of Iris.
 #
@@ -162,8 +162,8 @@ def _unrotate_equation(rotated_lons, rotated_lats,
                    np.sin(np.radians(trueLongitude) - lambda_angle) *
                    np.cos(phi_angle))
         sin_rot = -((np.sin(np.radians(trueLongitude) - lambda_angle) *
-                     np.sin(phi_angle))
-                    / np.cos(np.radians(rotated_lats)))
+                     np.sin(phi_angle)) /
+                    np.cos(np.radians(rotated_lats)))
 
         # Matrix-multiply to rotate the vectors.
         u_true = rotated_us * cos_rot - rotated_vs * sin_rot
diff --git a/lib/iris/tests/unit/analysis/regrid/test_RectilinearRegridder.py b/lib/iris/tests/unit/analysis/regrid/test_RectilinearRegridder.py
index 6b2aa23a41..a307603bad 100644
--- a/lib/iris/tests/unit/analysis/regrid/test_RectilinearRegridder.py
+++ b/lib/iris/tests/unit/analysis/regrid/test_RectilinearRegridder.py
@@ -46,10 +46,13 @@ def setUp(self):
         self.y = DimCoord(np.linspace(0, 49, 50))
         self.xs, self.ys = np.meshgrid(self.x.points, self.y.points)
 
-        transformation = lambda x, y: x + y ** 2
+        def transformation(x, y):
+            return x + y ** 2
+
         # Construct a function which adds dimensions to the 2D data array
         # so that we can test higher dimensional functionality.
-        dim_extender = lambda arr: (arr[np.newaxis, ..., np.newaxis] * [1, 2])
+        def dim_extender(arr):
+            return arr[np.newaxis, ..., np.newaxis] * [1, 2]
 
         self.data = dim_extender(transformation(self.xs, self.ys))
 
diff --git a/lib/iris/tests/unit/coord_categorisation/test_add_categorised_coord.py b/lib/iris/tests/unit/coord_categorisation/test_add_categorised_coord.py
index 3d78b06fb8..de21b9a0eb 100644
--- a/lib/iris/tests/unit/coord_categorisation/test_add_categorised_coord.py
+++ b/lib/iris/tests/unit/coord_categorisation/test_add_categorised_coord.py
@@ -1,4 +1,4 @@
-# (C) British Crown Copyright 2013 - 2015, Met Office
+# (C) British Crown Copyright 2013 - 2016, Met Office
 #
 # This file is part of Iris.
 #
@@ -49,7 +49,8 @@ def test_vectorise_call(self):
         # numpy.vectorize, before being applied to the points array.
         # The reason we use numpy.vectorize is to support multi-dimensional
         # coordinate points.
-        fn = lambda coord, v: v**2
+        def fn(coord, v):
+            return v**2
 
         with mock.patch('numpy.vectorize',
                         return_value=self.vectorised) as vectorise_patch:
@@ -75,7 +76,8 @@ def test_vectorise_call(self):
     def test_string_vectorised(self):
         # Check that special case handling of a vectorized string returning
         # function is taking place.
-        fn = lambda coord, v: '0123456789'[:v]
+        def fn(coord, v):
+            return '0123456789'[:v]
 
         with mock.patch('numpy.vectorize',
                         return_value=self.vectorised) as vectorise_patch:
diff --git a/lib/iris/tests/unit/cube/test_Cube.py b/lib/iris/tests/unit/cube/test_Cube.py
index f68214e4f2..4b51bc53b0 100644
--- a/lib/iris/tests/unit/cube/test_Cube.py
+++ b/lib/iris/tests/unit/cube/test_Cube.py
@@ -327,8 +327,7 @@ def setUp(self):
         self.mock_agg.aggregate = mock.Mock(
             return_value=mock.Mock(dtype='object'))
         self.mock_agg.aggregate_shape = mock.Mock(return_value=())
-        post_process_func = lambda x, y, z: x
-        self.mock_agg.post_process = mock.Mock(side_effect=post_process_func)
+        self.mock_agg.post_process = mock.Mock(side_effect=lambda x, y, z: x)
 
     def test_string_coord_agg_by_label(self):
         # Aggregate a cube on a string coordinate label where label
@@ -379,8 +378,7 @@ def setUp(self):
         self.mock_agg = mock.Mock(spec=Aggregator)
         self.mock_agg.aggregate = mock.Mock(
             return_value=np.empty([4]))
-        post_process_func = lambda x, y, z: x
-        self.mock_agg.post_process = mock.Mock(side_effect=post_process_func)
+        self.mock_agg.post_process = mock.Mock(side_effect=lambda x, y, z: x)
 
     def test_string_coord(self):
         # Rolling window on a cube that contains a string coordinate.
diff --git a/lib/iris/tests/unit/fileformats/grib/load_convert/test_convert.py b/lib/iris/tests/unit/fileformats/grib/load_convert/test_convert.py
index b93e185262..2ab05af4f4 100644
--- a/lib/iris/tests/unit/fileformats/grib/load_convert/test_convert.py
+++ b/lib/iris/tests/unit/fileformats/grib/load_convert/test_convert.py
@@ -1,4 +1,4 @@
-# (C) British Crown Copyright 2014 - 2015, Met Office
+# (C) British Crown Copyright 2014 - 2016, Met Office
 #
 # This file is part of Iris.
 #
@@ -35,7 +35,10 @@ def test_call(self):
         field = _make_test_message(sections)
         this = 'iris.fileformats.grib._load_convert.grib2_convert'
         factory = mock.sentinel.factory
-        func = lambda field, metadata: metadata['factories'].append(factory)
+
+        def func(field, metadata):
+            return metadata['factories'].append(factory)
+
         with mock.patch(this, side_effect=func) as grib2_convert:
             # The call being tested.
             result = convert(field)
diff --git a/lib/iris/tests/unit/fileformats/grib/load_convert/test_grid_definition_template_5.py b/lib/iris/tests/unit/fileformats/grib/load_convert/test_grid_definition_template_5.py
index 5fb8b53784..e799bf4d72 100644
--- a/lib/iris/tests/unit/fileformats/grib/load_convert/test_grid_definition_template_5.py
+++ b/lib/iris/tests/unit/fileformats/grib/load_convert/test_grid_definition_template_5.py
@@ -1,4 +1,4 @@
-# (C) British Crown Copyright 2014 - 2015, Met Office
+# (C) British Crown Copyright 2014 - 2016, Met Office
 #
 # This file is part of Iris.
 #
@@ -50,8 +50,11 @@ def setUp(self):
         self.coord = mock.sentinel.coord
         self.dim = mock.sentinel.dim
         item = (self.coord, self.dim)
-        func = lambda s, m, y, x, c: m['dim_coords_and_dims'].append(item)
+
+        def func(s, m, y, x, c):
+            return m['dim_coords_and_dims'].append(item)
         patch.append(mock.patch(this, side_effect=func))
+
         this = 'iris.coord_systems.RotatedGeogCS'
         self.cs = mock.sentinel.cs
         patch.append(mock.patch(this, return_value=self.cs))
diff --git a/lib/iris/tests/unit/fileformats/grib/load_convert/test_product_definition_template_1.py b/lib/iris/tests/unit/fileformats/grib/load_convert/test_product_definition_template_1.py
index 47a832e9a9..d8c8f5344e 100644
--- a/lib/iris/tests/unit/fileformats/grib/load_convert/test_product_definition_template_1.py
+++ b/lib/iris/tests/unit/fileformats/grib/load_convert/test_product_definition_template_1.py
@@ -1,4 +1,4 @@
-# (C) British Crown Copyright 2014 - 2015, Met Office
+# (C) British Crown Copyright 2014 - 2016, Met Office
 #
 # This file is part of Iris.
 #
@@ -41,8 +41,11 @@ def setUp(self):
         self.patch('warnings.warn')
         this = '{}.product_definition_template_0'.format(module)
         self.cell_method = mock.sentinel.cell_method
-        func = lambda s, m, f: m['cell_methods'].append(self.cell_method)
+
+        def func(s, m, f):
+            return m['cell_methods'].append(self.cell_method)
         self.patch(this, side_effect=func)
+
         self.metadata = {'factories': [], 'references': [],
                          'standard_name': None,
                          'long_name': None, 'units': None, 'attributes': {},
diff --git a/lib/iris/tests/unit/fileformats/grib/load_convert/test_product_definition_template_11.py b/lib/iris/tests/unit/fileformats/grib/load_convert/test_product_definition_template_11.py
index e2e3457d77..a20cb4cf75 100644
--- a/lib/iris/tests/unit/fileformats/grib/load_convert/test_product_definition_template_11.py
+++ b/lib/iris/tests/unit/fileformats/grib/load_convert/test_product_definition_template_11.py
@@ -41,8 +41,11 @@ def setUp(self):
         self.patch('warnings.warn')
         this_module = '{}.product_definition_template_11'.format(module)
         self.cell_method = mock.sentinel.cell_method
-        func = lambda s, m, f: m['cell_methods'].append(self.cell_method)
+
+        def func(s, m, f):
+            return m['cell_methods'].append(self.cell_method)
         self.patch(this_module, side_effect=func)
+
         self.patch_statistical_fp_coord = self.patch(
             module + '.statistical_forecast_period_coord',
             return_value=mock.sentinel.dummy_fp_coord)
diff --git a/lib/iris/tests/unit/fileformats/grib/load_convert/test_product_definition_template_31.py b/lib/iris/tests/unit/fileformats/grib/load_convert/test_product_definition_template_31.py
index b06fa7145b..59f6f327f8 100644
--- a/lib/iris/tests/unit/fileformats/grib/load_convert/test_product_definition_template_31.py
+++ b/lib/iris/tests/unit/fileformats/grib/load_convert/test_product_definition_template_31.py
@@ -1,4 +1,4 @@
-# (C) British Crown Copyright 2014 - 2015, Met Office
+# (C) British Crown Copyright 2014 - 2016, Met Office
 #
 # This file is part of Iris.
 #
@@ -64,7 +64,11 @@ def _check(self, request_warning=False, value=10, factor=1):
         with mock.patch(this, warn_on_unsupported=request_warning):
             # The call being tested.
             product_definition_template_31(section, metadata, rt_coord)
+
         # Check the result.
+        def unscale(v, f):
+            return v / 10.0 ** f
+
         expected = deepcopy(self.metadata)
         coord = AuxCoord(series, long_name='satellite_series')
         expected['aux_coords_and_dims'].append((coord, None))
@@ -72,7 +76,6 @@ def _check(self, request_warning=False, value=10, factor=1):
         expected['aux_coords_and_dims'].append((coord, None))
         coord = AuxCoord(instrument, long_name='instrument_type')
         expected['aux_coords_and_dims'].append((coord, None))
-        unscale = lambda v, f: v / 10.0 ** f
         standard_name = 'sensor_band_central_radiation_wavenumber'
         coord = AuxCoord(unscale(value, factor),
                          standard_name=standard_name,
diff --git a/lib/iris/tests/unit/fileformats/grib/load_convert/test_vertical_coords.py b/lib/iris/tests/unit/fileformats/grib/load_convert/test_vertical_coords.py
index 5775502b98..51f5c68407 100644
--- a/lib/iris/tests/unit/fileformats/grib/load_convert/test_vertical_coords.py
+++ b/lib/iris/tests/unit/fileformats/grib/load_convert/test_vertical_coords.py
@@ -1,4 +1,4 @@
-# (C) British Crown Copyright 2014 - 2015, Met Office
+# (C) British Crown Copyright 2014 - 2016, Met Office
 #
 # This file is part of Iris.
 #
@@ -50,7 +50,10 @@ def test_hybrid_factories(self):
         section = {'NV': 1}
         this = 'iris.fileformats.grib._load_convert.hybrid_factories'
         factory = mock.sentinel.factory
-        func = lambda section, metadata: metadata['factories'].append(factory)
+
+        def func(section, metadata):
+            return metadata['factories'].append(factory)
+
         with mock.patch(this, side_effect=func) as hybrid_factories:
             vertical_coords(section, metadata)
             self.assertTrue(hybrid_factories.called)
diff --git a/lib/iris/tests/unit/fileformats/pyke_rules/compiled_krb/fc_rules_cf_fc/test_reorder_bounds_data.py b/lib/iris/tests/unit/fileformats/pyke_rules/compiled_krb/fc_rules_cf_fc/test_reorder_bounds_data.py
index cb0786af88..4c8b562dc6 100644
--- a/lib/iris/tests/unit/fileformats/pyke_rules/compiled_krb/fc_rules_cf_fc/test_reorder_bounds_data.py
+++ b/lib/iris/tests/unit/fileformats/pyke_rules/compiled_krb/fc_rules_cf_fc/test_reorder_bounds_data.py
@@ -1,4 +1,4 @@
-# (C) British Crown Copyright 2014 - 2015, Met Office
+# (C) British Crown Copyright 2014 - 2016, Met Office
 #
 # This file is part of Iris.
 #
@@ -58,8 +58,7 @@ def test_slowest_varying(self):
 
     def test_slowest_varying_lazy(self):
         bounds_data = np.arange(24).reshape(4, 2, 3)
-        func = lambda: bounds_data
-        lazy_bounds_data = _LazyArray(bounds_data.shape, func,
+        lazy_bounds_data = _LazyArray(bounds_data.shape, lambda: bounds_data,
                                       bounds_data.dtype)
         cf_bounds_var = mock.Mock(dimensions=('nv', 'foo', 'bar'))
         cf_coord_var = mock.Mock(dimensions=('foo', 'bar'))
diff --git a/lib/iris/tests/unit/fileformats/test_rules.py b/lib/iris/tests/unit/fileformats/test_rules.py
index a41d1b48a7..b815b0fece 100644
--- a/lib/iris/tests/unit/fileformats/test_rules.py
+++ b/lib/iris/tests/unit/fileformats/test_rules.py
@@ -52,7 +52,9 @@ def test_attributes(self):
         self.assertEqual(target.name, 'foo')
         self.assertIsNone(target.transform)
 
-        transform = lambda _: _
+        def transform(_):
+            return _
+
         target = ConcreteReferenceTarget('foo', transform)
         self.assertEqual(target.name, 'foo')
         self.assertIs(target.transform, transform)
@@ -64,7 +66,9 @@ def test_single_cube_no_transform(self):
         self.assertIs(target.as_cube(), src)
 
     def test_single_cube_with_transform(self):
-        transform = lambda cube: {'long_name': 'wibble'}
+        def transform(cube):
+            return {'long_name': 'wibble'}
+
         target = ConcreteReferenceTarget('foo', transform)
         src = stock.simple_2d()
         target.add_cube(src)
@@ -84,7 +88,9 @@ def test_multiple_cubes_no_transform(self):
         self.assertEqual(dest, src)
 
     def test_multiple_cubes_with_transform(self):
-        transform = lambda cube: {'long_name': 'wibble'}
+        def transform(cube):
+            return {'long_name': 'wibble'}
+
         target = ConcreteReferenceTarget('foo', transform)
         src = stock.realistic_4d()
         for i in range(src.shape[0]):
@@ -104,7 +110,10 @@ def test_simple_factory(self):
         # The fake PPField which will be supplied to our converter.
         field = Mock()
         field.data = None
-        field_generator = lambda filename: [field]
+
+        def field_generator(filename):
+            return [field]
+
         # A fake conversion function returning:
         #   1) A parameter cube needing a simple factory construction.
         aux_factory = Mock()
@@ -167,7 +176,10 @@ def test_cross_reference(self):
         press_field.data = param_cube.data
         orog_field = Mock()
         orog_field.data = orog_cube.data
-        field_generator = lambda filename: [press_field, orog_field]
+
+        def field_generator(filename):
+            return [press_field, orog_field]
+
         # A fake rule set returning:
         #   1) A parameter cube needing an "orography" reference
         #   2) An "orography" cube
diff --git a/lib/iris/unit.py b/lib/iris/unit.py
index 81f83c4321..7ccc251af0 100644
--- a/lib/iris/unit.py
+++ b/lib/iris/unit.py
@@ -1871,8 +1871,7 @@ def convert(self, value, other, ctype=FLOAT64):
                 ut2 = other.utime()
                 result = ut2.date2num(ut1.num2date(value_copy))
                 # Preserve the datatype of the input array if it was float32.
-                if (isinstance(value, np.ndarray)
-                        and value.dtype == np.float32):
+                if isinstance(value, np.ndarray) and value.dtype == np.float32:
                     result = result.astype(np.float32)
             else:
                 ut_converter = _ut_get_converter(self.ut_unit, other.ut_unit)
diff --git a/lib/iris/util.py b/lib/iris/util.py
index e85b658912..ebb6bfa746 100644
--- a/lib/iris/util.py
+++ b/lib/iris/util.py
@@ -306,8 +306,8 @@ def guess_coord_axis(coord):
     elif coord.standard_name in ('latitude', 'grid_latitude',
                                  'projection_y_coordinate'):
         axis = 'Y'
-    elif (coord.units.is_convertible('hPa')
-          or coord.attributes.get('positive') in ('up', 'down')):
+    elif (coord.units.is_convertible('hPa') or
+          coord.attributes.get('positive') in ('up', 'down')):
         axis = 'Z'
     elif coord.units.is_time_reference():
         axis = 'T'
@@ -598,8 +598,9 @@ def column_slices_generator(full_slice, ndims):
 
     # Get all of the dimensions for which a tuple of indices were provided
     # (numpy.ndarrays are treated in the same way tuples in this case)
-    is_tuple_style_index = lambda key: isinstance(key, tuple) or \
-        (isinstance(key, np.ndarray) and key.ndim == 1)
+    def is_tuple_style_index(key):
+        return (isinstance(key, tuple) or
+                (isinstance(key, np.ndarray) and key.ndim == 1))
     tuple_indices = [i for i, key in enumerate(full_slice)
                      if is_tuple_style_index(key)]
 
diff --git a/minimal-conda-requirements.txt b/minimal-conda-requirements.txt
index 5aef25c0f8..bf517e5f19 100644
--- a/minimal-conda-requirements.txt
+++ b/minimal-conda-requirements.txt
@@ -17,7 +17,7 @@ setuptools
 # Iris testing/documentation dependencies
 mock
 nose
-pep8=1.5.7
+pep8
 sphinx
 filelock