diff --git a/Gemfile.lock b/Gemfile.lock
index d128655f1..87d0673cf 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -162,7 +162,7 @@ GEM
     govuk_personalisation (0.16.0)
       plek (>= 1.9.0)
       rails (>= 6, < 8)
-    govuk_publishing_components (39.2.5)
+    govuk_publishing_components (40.0.0)
       govuk_app_config
       govuk_personalisation (>= 0.7.0)
       kramdown
diff --git a/app/assets/config/manifest.js b/app/assets/config/manifest.js
index 1b6313e59..7cb2ec743 100644
--- a/app/assets/config/manifest.js
+++ b/app/assets/config/manifest.js
@@ -1,4 +1,5 @@
 //= link_tree ../images
 //= link application.js
+//= link es6-components.js
 //= link webchat.js
 //= link_tree ../builds
diff --git a/app/assets/javascripts/application.js b/app/assets/javascripts/application.js
index fdd109291..3110fcc69 100644
--- a/app/assets/javascripts/application.js
+++ b/app/assets/javascripts/application.js
@@ -1,13 +1,10 @@
 //= require govuk_publishing_components/lib
-//= require govuk_publishing_components/components/accordion
 //= require govuk_publishing_components/components/details
-//= require govuk_publishing_components/components/error-summary
 //= require govuk_publishing_components/components/govspeak
 //= require govuk_publishing_components/components/image-card
 //= require govuk_publishing_components/components/intervention
 //= require govuk_publishing_components/components/metadata
 //= require govuk_publishing_components/components/print-link
-//= require govuk_publishing_components/components/radio
 //= require govuk_publishing_components/components/single-page-notification-button
 //= require govuk_publishing_components/components/step-by-step-nav
 
diff --git a/app/assets/javascripts/es6-components.js b/app/assets/javascripts/es6-components.js
new file mode 100644
index 000000000..d5bc4c711
--- /dev/null
+++ b/app/assets/javascripts/es6-components.js
@@ -0,0 +1,12 @@
+// These modules from govuk_publishing_components
+// depend on govuk-frontend modules. govuk-frontend
+// now targets browsers that support `type="module"`.
+//
+// To gracefully prevent execution of these scripts
+// on browsers that don't support ES6, this script
+// should be included in a `type="module"` script tag
+// which will ensure they are never loaded.
+
+//= require govuk_publishing_components/components/accordion
+//= require govuk_publishing_components/components/error-summary
+//= require govuk_publishing_components/components/radio
diff --git a/app/assets/stylesheets/application.scss b/app/assets/stylesheets/application.scss
index 5f3f96f13..1b1c78da7 100644
--- a/app/assets/stylesheets/application.scss
+++ b/app/assets/stylesheets/application.scss
@@ -1,8 +1,4 @@
 // The main application stylesheet
-$govuk-compatibility-govuktemplate: false;
-$govuk-typography-use-rem: false;
-$govuk-use-legacy-palette: false;
-$govuk-new-link-styles: true;
 
 // This flag stops the font from being included in this application's
 // stylesheet - the font is being served by Static across all of GOV.UK, so is
diff --git a/app/assets/stylesheets/components/_contents-list-with-body.scss b/app/assets/stylesheets/components/_contents-list-with-body.scss
index e7dc44966..f38e8bf5f 100644
--- a/app/assets/stylesheets/components/_contents-list-with-body.scss
+++ b/app/assets/stylesheets/components/_contents-list-with-body.scss
@@ -23,7 +23,7 @@
 }
 
 .app-c-contents-list-with-body__link-wrapper.sticky-element--stuck-to-window {
-  background-color: govuk-colour("light-grey", $legacy: "grey-3");
+  background-color: govuk-colour("light-grey");
   bottom: -1px; // 'Fix' for anomalous 1px margin which sporadically appears below this element.
   left: 0;
   margin: 0;
diff --git a/app/assets/stylesheets/helpers/_parts.scss b/app/assets/stylesheets/helpers/_parts.scss
index 4837e7b4a..97d97960c 100644
--- a/app/assets/stylesheets/helpers/_parts.scss
+++ b/app/assets/stylesheets/helpers/_parts.scss
@@ -9,7 +9,7 @@
       margin-bottom: 0;
     }
 
-    border-bottom: 1px solid govuk-colour("mid-grey", $legacy: "grey-2");
+    border-bottom: 1px solid govuk-colour("mid-grey");
   }
 
   .part-navigation {
diff --git a/app/assets/stylesheets/views/_manual.scss b/app/assets/stylesheets/views/_manual.scss
index d387a4297..d3a94a6f0 100644
--- a/app/assets/stylesheets/views/_manual.scss
+++ b/app/assets/stylesheets/views/_manual.scss
@@ -61,7 +61,7 @@
   list-style: none;
 
   &:hover {
-    background-color: govuk-colour("light-grey", $legacy: "grey-4");
+    background-color: govuk-colour("light-grey");
   }
 
   &:last-child {
diff --git a/app/views/layouts/application.html.erb b/app/views/layouts/application.html.erb
index cb7dc363a..b8a944baf 100644
--- a/app/views/layouts/application.html.erb
+++ b/app/views/layouts/application.html.erb
@@ -49,6 +49,7 @@
 
   <%= stylesheet_link_tag "application", :media => "all", integrity: false %>
   <%= javascript_include_tag "application", integrity: false %>
+  <%= javascript_include_tag 'es6-components', type: "module" %>
   <%= csrf_meta_tags %>
   <%= render 'govuk_publishing_components/components/meta_tags', content_item: @content_item.content_item %>
 
diff --git a/test/integration/service_manual_phase_label_test.rb b/test/integration/service_manual_phase_label_test.rb
index d321b3f03..728e36666 100644
--- a/test/integration/service_manual_phase_label_test.rb
+++ b/test/integration/service_manual_phase_label_test.rb
@@ -29,7 +29,7 @@ class ServiceManualPhaseLabelTest < ActionDispatch::IntegrationTest
     stub_content_store_has_item(guide["base_path"], guide)
     visit guide["base_path"]
 
-    assert_text("ALPHA")
+    assert_text("Alpha")
   end
 
   test "No phase label is displayed for a guide without a phase field" do