diff --git a/docs/src/_templates/layout.html b/docs/src/_templates/layout.html
index 9a6fe46d01..974bd12753 100644
--- a/docs/src/_templates/layout.html
+++ b/docs/src/_templates/layout.html
@@ -11,7 +11,7 @@
         <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-right of the screen.
+            via the flyout menu in the bottom corner of the screen.
         </div>
         <p></p>
     {%- endif %}
diff --git a/docs/src/conf.py b/docs/src/conf.py
index d1ec7bab3b..ae5a32e8a3 100644
--- a/docs/src/conf.py
+++ b/docs/src/conf.py
@@ -310,6 +310,9 @@ def _dotv(version):
     ],
     "use_edit_page_button": True,
     "show_toc_level": 1,
+    # Omitted `theme-switcher` below to disable it
+    # Info: https://pydata-sphinx-theme.readthedocs.io/en/stable/user_guide/light-dark.html#configure-default-theme-mode
+    "navbar_end": ["navbar-icon-links"],
 }
 
 rev_parse = run(["git", "rev-parse", "--short", "HEAD"], capture_output=True)
@@ -321,6 +324,9 @@ def _dotv(version):
     "github_user": "scitools",
     "github_version": "main",
     "doc_path": "docs/src",
+    # default theme.  Also disabled the button in the html_theme_options.
+    # Info: https://pydata-sphinx-theme.readthedocs.io/en/stable/user_guide/light-dark.html#configure-default-theme-mode
+    "default_mode": "light",
     # custom
     "on_rtd": on_rtd,
     "rtd_version": rtd_version,
diff --git a/docs/src/whatsnew/latest.rst b/docs/src/whatsnew/latest.rst
index d1aae76675..b0569ed673 100644
--- a/docs/src/whatsnew/latest.rst
+++ b/docs/src/whatsnew/latest.rst
@@ -68,6 +68,9 @@ This document explains the changes made to Iris for this release
 ================
 
 #. `@rcomer`_ clarified instructions for updating gallery tests. (:pull:`5100`)
+#. `@tkknight`_ unpinned ``pydata-sphinx-theme`` and set the default to use
+   the light version (not dark) while we make the docs dark mode friendly
+   (:pull:`5129`)
 
 
 💼 Internal
diff --git a/requirements/ci/py310.yml b/requirements/ci/py310.yml
index 6815c7fe6d..d79015c055 100644
--- a/requirements/ci/py310.yml
+++ b/requirements/ci/py310.yml
@@ -48,7 +48,7 @@ dependencies:
   - sphinx-copybutton
   - sphinx-gallery >=0.11.0
   - sphinx-panels
-  - pydata-sphinx-theme = 0.8.1
+  - pydata-sphinx-theme
 
 # Temporary minimum pins.
 # See https://github.com/SciTools/iris/pull/5051
diff --git a/requirements/ci/py38.yml b/requirements/ci/py38.yml
index 316e0868ac..b68e8ccf45 100644
--- a/requirements/ci/py38.yml
+++ b/requirements/ci/py38.yml
@@ -48,7 +48,7 @@ dependencies:
   - sphinx-copybutton
   - sphinx-gallery >=0.11.0
   - sphinx-panels
-  - pydata-sphinx-theme = 0.8.1
+  - pydata-sphinx-theme
 
 # Temporary minimum pins.
 # See https://github.com/SciTools/iris/pull/5051
diff --git a/requirements/ci/py39.yml b/requirements/ci/py39.yml
index 66e22c230f..9fec76cfde 100644
--- a/requirements/ci/py39.yml
+++ b/requirements/ci/py39.yml
@@ -48,7 +48,7 @@ dependencies:
   - sphinx-copybutton
   - sphinx-gallery >=0.11.0
   - sphinx-panels
-  - pydata-sphinx-theme = 0.8.1
+  - pydata-sphinx-theme
 
 # Temporary minimum pins.
 # See https://github.com/SciTools/iris/pull/5051