diff --git a/docs/src/_templates/layout.html b/docs/src/_templates/layout.html
deleted file mode 100644
index 974bd12753..0000000000
--- a/docs/src/_templates/layout.html
+++ /dev/null
@@ -1,20 +0,0 @@
-{% extends "pydata_sphinx_theme/layout.html" %}
-
-{# This uses blocks.  See:
-     https://www.sphinx-doc.org/en/master/templating.html
-#}
-
-
-    {%- block docs_body %}
-
-    {% if on_rtd and rtd_version == 'latest' %}
-        <div id="slim-red-box-banner">
-            You are viewing the <b>latest</b> unreleased documentation
-            <b>v{{ version }}</b>. You can switch to a <b>stable</b> version
-            via the flyout menu in the bottom corner of the screen.
-        </div>
-        <p></p>
-    {%- endif %}
-
-    {{ super() }}
-{%- endblock %}
diff --git a/docs/src/conf.py b/docs/src/conf.py
index 7f7322c1f8..5b3fd9433b 100644
--- a/docs/src/conf.py
+++ b/docs/src/conf.py
@@ -329,6 +329,16 @@ def _dotv(version):
     },
 }
 
+# if we are building via Read The Docs and it is the latest (not stable)
+if on_rtd and rtd_version == "latest":
+    html_theme_options[
+        "announcement"
+    ] = f"""
+        You are viewing the <b>latest</b> unreleased documentation
+        <strong>{version}</strong>. You can switch to a
+        <a href="https://scitools-iris.readthedocs.io/en/stable/">stable</a>
+        version."""
+
 rev_parse = run(["git", "rev-parse", "--short", "HEAD"], capture_output=True)
 commit_sha = rev_parse.stdout.decode().strip()