diff --git a/docs/src/whatsnew/3.6.rst b/docs/src/whatsnew/3.6.rst
index 61bf75f15c..136d47e15d 100644
--- a/docs/src/whatsnew/3.6.rst
+++ b/docs/src/whatsnew/3.6.rst
@@ -63,6 +63,11 @@ This document explains the changes made to Iris for this release
    :icon: alert
    :animate: fade-in
 
+   📢 **Announcements**
+
+   Welcome and congratulations to `@sloosvel`_ who made their first contribution to
+   Iris! 🎉
+
    The patches in this release of Iris include:
 
    🐛 **Bugs Fixed**
@@ -76,6 +81,15 @@ This document explains the changes made to Iris for this release
       properly updated.
       (:issue:`5339`, :pull:`5340`)
 
+   🚀 **Performance Enhancements**
+
+   #. `@sloosvel`_ improved :meth:`~iris.cube.CubeList.concatenate_cube` and
+      :meth:`~iris.cube.CubeList.concatenate` to ensure that lazy auxiliary coordinate
+      points and bounds are not realized. This change now allows cubes with
+      high-resolution auxiliary coordinates to concatenate successfully whilst using a
+      minimal in-core memory footprint.
+      (:issue:`5115`, :pull:`5142`)
+
 
 📢 Announcements
 ================
@@ -191,6 +205,7 @@ This document explains the changes made to Iris for this release
     core dev names are automatically included by the common_links.inc:
 
 .. _@fnattino: https://github.com/fnattino
+.. _@sloosvel: https://github.com/sloosvel
 
 
 .. comment