diff --git a/CHANGELOG.md b/CHANGELOG.md
index 7f65d82..ef159b6 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -11,8 +11,12 @@
 
 - (Dan) Updates ruby version to 2.7.8 and alpine version to 3.16 [GH-143](https://github.com/epimorphics/standard-reports-ui/issues/143)
 
-## 1.5.4 - 2024-09
+## 1.5.4 - 2024-10
 
+- (Jon) Wrapped the Internal Error Instrumentation in an `unless` block to
+  ensure the application does not report internal errors to the Prometheus
+  metrics when the error is a 404 or 422 thereby reducing the noise in the Slack
+  alerts channel
 - (Jon) Updated the application exceptions controller to instrument the
   `ActiveSupport::Notifications` for internal errors
   [GH-139](https://github.com/epimorphics/standard-reports-ui/issues/139)
diff --git a/app/controllers/application_controller.rb b/app/controllers/application_controller.rb
index 31e9aca..5776c10 100644
--- a/app/controllers/application_controller.rb
+++ b/app/controllers/application_controller.rb
@@ -27,8 +27,10 @@ def log_request_result
   # or attempt to render a generic error page if no specific error page exists
   unless Rails.application.config.consider_all_requests_local
     rescue_from StandardError do |e|
-      # Instrument ActiveSupport::Notifications for internal errors:
-      ActiveSupport::Notifications.instrument('internal_error.application', exception: e)
+      # Instrument ActiveSupport::Notifications for internal errors but only for non-404 errors:
+      unless e.is_a?(ActionController::RoutingError) || e.is_a?(ActionView::MissingTemplate)
+        ActiveSupport::Notifications.instrument('internal_error.application', exception: e)
+      end
       # Trigger the appropriate error handling method based on the exception
       case e.class
       when ActionController::RoutingError, ActionView::MissingTemplate
@@ -104,7 +106,7 @@ def detailed_request_log(duration)
       body: request.body.gets&.gsub("\n", '\n'),
       method: request.method,
       status: response.status,
-      message: Rack::Utils::HTTP_STATUS_CODES[response.status]
+      message: response.message || Rack::Utils::HTTP_STATUS_CODES[response.status]
     }
 
     case response.status