diff --git a/medcat/utils/preprocess_snomed.py b/medcat/utils/preprocess_snomed.py
index 3ba94b977..1e6efcb79 100644
--- a/medcat/utils/preprocess_snomed.py
+++ b/medcat/utils/preprocess_snomed.py
@@ -35,6 +35,32 @@ def get_all_children(sctid, pt2ch):
     return result
 
 
+def get_direct_refset_mapping(in_dict: dict) -> dict:
+    """This method uses the output from Snomed.map_snomed2icd10 or
+    Snomed.map_snomed2opcs4 and removes the metadata and maps each
+    SNOMED CUI to the prioritised list of the target ontology CUIs.
+
+    The input dict is expected to be in the following format:
+    - Keys are SnomedCT CUIs
+    - The values are lists of dictionaries, each list item (at least)
+      - Has a key 'code' that specifies the target onotlogy CUI
+      - Has a key 'mapPriority' that specifies the priority
+
+    Args:
+        in_dict (dict): The input dict.
+
+    Returns:
+        dict: The map from Snomed CUI to list of priorities list of target ontology CUIs.
+    """
+    ret_dict = dict()
+    for k, vals in in_dict.items():
+        # sort such that highest priority values are first
+        svals = sorted(vals, key=lambda el: el['mapPriority'], reverse=True)
+        # only keep the code / CUI
+        ret_dict[k] = [v['code'] for v in svals]
+    return ret_dict
+
+
 class Snomed:
     """
     Pre-process SNOMED CT release files.
@@ -53,6 +79,15 @@ def __init__(self, data_path, uk_ext=False, uk_drug_ext=False):
         self.release = data_path[-16:-8]
         self.uk_ext = uk_ext
         self.uk_drug_ext = uk_drug_ext
+        self.opcs_refset_id = "1126441000000105"
+        if ((self.uk_ext or self.uk_drug_ext) and
+                # using lexicographical comparison below
+                # e.g "20240101" > "20231122" results in True
+                # yet "20231121" > "20231122" reults in False
+                len(self.release) == len("20231122") and self.release >= "20231122"):
+            # NOTE for UK extensions starting from 20231122 the
+            #      OPCS4 refset ID seems to be different
+            self.opcs_refset_id = '1382401000000109'
 
     def to_concept_df(self):
         """
@@ -398,7 +433,7 @@ def _map_snomed2refset(self):
         mapping_df = pd.concat(dfs2merge)
         del dfs2merge
         if self.uk_ext or self.uk_drug_ext:
-            opcs_df = mapping_df[mapping_df['refsetId'] == '1126441000000105']
+            opcs_df = mapping_df[mapping_df['refsetId'] == self.opcs_refset_id]
             icd10_df = mapping_df[mapping_df['refsetId']
                                   == '999002271000000101']
             return icd10_df, opcs_df
diff --git a/tests/utils/test_preprocess_snomed.py b/tests/utils/test_preprocess_snomed.py
new file mode 100644
index 000000000..59a00f6fc
--- /dev/null
+++ b/tests/utils/test_preprocess_snomed.py
@@ -0,0 +1,64 @@
+from typing import Dict
+from medcat.utils import preprocess_snomed
+
+import unittest
+
+
+EXAMPLE_REFSET_DICT: Dict = {
+   'SCUI1': [
+       {'code': 'TCUI1', 'mapPriority': '1'},
+       {'code': 'TCUI2', 'mapPriority': '2'},
+       {'code': 'TCUI3', 'mapPriority': '3'},
+       ]
+}
+
+# in order from highest priority to lowest
+EXPECTED_DIRECT_MAPPINGS = {"SCUI1": ['TCUI3', 'TCUI2', 'TCUI1']}
+
+EXAMPLE_REFSET_DICT_WITH_EXTRAS = dict(
+    (k, [dict(v, otherKey=f"val-{k}") for v in vals]) for k, vals in EXAMPLE_REFSET_DICT.items())
+
+EXAMPLE_REFSET_DICT_NO_PRIORITY = dict(
+    (k, [{ik: iv for ik, iv in v.items() if ik != 'mapPriority'} for v in vals]) for k, vals in EXAMPLE_REFSET_DICT.items()
+)
+
+EXAMPLE_REFSET_DICT_NO_CODE = dict(
+    (k, [{ik: iv for ik, iv in v.items() if ik != 'code'} for v in vals]) for k, vals in EXAMPLE_REFSET_DICT.items()
+)
+
+
+class DirectMappingTest(unittest.TestCase):
+
+    def test_example_gets_direct_mappings(self):
+        res = preprocess_snomed.get_direct_refset_mapping(EXAMPLE_REFSET_DICT)
+        self.assertEqual(res, EXPECTED_DIRECT_MAPPINGS)
+
+    def test_example_w_extras_gets_direct_mappings(self):
+        res = preprocess_snomed.get_direct_refset_mapping(EXAMPLE_REFSET_DICT_WITH_EXTRAS)
+        self.assertEqual(res, EXPECTED_DIRECT_MAPPINGS)
+
+    def test_example_no_priority_fails(self):
+        with self.assertRaises(KeyError):
+            preprocess_snomed.get_direct_refset_mapping(EXAMPLE_REFSET_DICT_NO_PRIORITY)
+
+    def test_example_no_codfe_fails(self):
+        with self.assertRaises(KeyError):
+            preprocess_snomed.get_direct_refset_mapping(EXAMPLE_REFSET_DICT_NO_CODE)
+
+EXAMPLE_SNOMED_PATH_OLD = "SnomedCT_InternationalRF2_PRODUCTION_20220831T120000Z"
+EXAMPLE_SNOMED_PATH_NEW = "SnomedCT_UKClinicalRF2_PRODUCTION_20231122T000001Z"
+
+
+class TestSnomedVersionsOPCS4(unittest.TestCase):
+
+    def test_old_gets_old_OPCS4_mapping_nonuk_ext(self):
+        snomed = preprocess_snomed.Snomed(EXAMPLE_SNOMED_PATH_OLD, uk_ext=False)
+        self.assertEqual(snomed.opcs_refset_id, "1126441000000105")
+
+    def test_old_gets_old_OPCS4_mapping_uk_ext(self):
+        snomed = preprocess_snomed.Snomed(EXAMPLE_SNOMED_PATH_OLD, uk_ext=True)
+        self.assertEqual(snomed.opcs_refset_id, "1126441000000105")
+
+    def test_new_gets_new_OCPS4_mapping_uk_ext(self):
+        snomed = preprocess_snomed.Snomed(EXAMPLE_SNOMED_PATH_NEW, uk_ext=True)
+        self.assertEqual(snomed.opcs_refset_id, "1382401000000109")