diff --git a/build.xml b/build.xml
index 8a6b34b1..aa4b4119 100644
--- a/build.xml
+++ b/build.xml
@@ -1522,13 +1522,13 @@
     -->
 
     <macrodef name="SLACK.send">
-        <attribute name="conf" />
-        <attribute name="colour" />
-        <attribute name="message" />
+        <attribute name="conf"/>
+        <attribute name="colour"/>
+        <attribute name="message"/>
         <sequential>
             <exec executable="bash" failonerror="true">
-                <arg value="-c" />
-                <arg value="echo -e '@{message}' | ${tools.slacktee}/bin/slacktee.sh -p --config @{conf} -a @{colour}" />
+                <arg value="-c"/>
+                <arg value="echo -e '@{message}' | ${tools.slacktee}/bin/slacktee.sh -p --config @{conf} -a @{colour}"/>
             </exec>
         </sequential>
     </macrodef>
@@ -1537,18 +1537,17 @@
         Send success notification to slack channel
     -->
     <target name="slack.notify.publication.success">
-        <tstamp>
-            <format property="DATE_UTC" pattern="yyyy-MM-dd" locale="UTC" />
-        </tstamp>
-        <tstamp>
-            <format property="TIME_UTC" pattern="HH:mm" locale="UTC" />
-        </tstamp>
         <!-- Only send when we're doing prod flows -->
         <if>
             <equals arg1="${env}" arg2="prod"/>
             <then>
+                <exec executable="bash" failonerror="true" outputproperty="diff.between.publications">
+                    <arg value="${utilities.dir}/diff-between-publications.sh"/>
+                    <arg value="${shared.ws.dir}/${git.repo.project.data}"/>
+                    <arg value="${shared.ws.dir}/${git.repo.project.products}"/>
+                </exec>
                 <SLACK.send conf="${tools.slacktee}/conf/aggr-ant.conf" colour="good"
-                    message="${DATE_UTC} ${TIME_UTC}: Successfully published new UKf MD Aggregates and MDQ cache." />
+                    message="${diff.between.publications}"/>
             </then>
         </if>
     </target>
diff --git a/utilities/diff-between-publications.sh b/utilities/diff-between-publications.sh
new file mode 100755
index 00000000..fb970764
--- /dev/null
+++ b/utilities/diff-between-publications.sh
@@ -0,0 +1,94 @@
+#!/bin/bash
+
+# This script will output details about the current UKf publication and 
+# the differences since the last.
+#
+# Expects the following to be provided as arguments:
+# * Absolute path to data repository
+# * Absolute path to products repository
+#
+# Assumes the data repository's master branch is currently checked out.
+#
+
+# Fail if $1 and $2 aren't provided.
+if [[ -z $1 && -z $2 ]]; then
+    echo "usage: git-diff-between-publications.sh <path to data repository> <path to products repository>"
+    exit 1
+fi
+
+# Get the input
+repodata=$1
+repoproducts=$2
+
+# =====
+# = First of all, we need to calculate some stuff.
+# =====
+
+# Figure out name of the latest tag and the previous tag.
+# These point to the latest, and previous, publication.
+currenttag=$(git --work-tree=$repoproducts --git-dir=$repoproducts/.git tag | tail -n 1)
+previoustag=$(git --work-tree=$repoproducts --git-dir=$repoproducts/.git tag | tail -n 2 | head -n 1)
+
+# Calculate current member count (the final awk is for Mac compatibility, since wc on Mac outputs leading spaces)
+membercount=$(grep 'Member ID' $repodata/members/members.xml | wc -l | awk '{print $1}')
+
+# Calculate current entities count (UK only)
+entitycountuk=$(grep 'registrationAuthority="http://ukfederation.org.uk"' $repoproducts/aggregates/ukfederation-metadata.xml | wc -l | awk '{print $1}')
+
+# Calculate current entities count (total, including all imported entities)
+entitycounttotal=$(grep '<EntityDescriptor' $repoproducts/aggregates/ukfederation-metadata.xml | wc -l | awk '{print $1}')
+
+# Calculate size of current aggregate, in bytes and MB
+currentaggregatesize=$(cat $repoproducts/aggregates/ukfederation-metadata.xml | wc -c)
+currentaggregatesizemb=$(echo "scale=2;$currentaggregatesize/1024/1024" | bc )
+
+# Calculate size of previous aggregate
+previousaggregatesize=$(git --work-tree=$repoproducts --git-dir=$repoproducts/.git show $previoustag:aggregates/ukfederation-metadata.xml | wc -c)
+previousaggregatesizemb=$(echo "scale=2;$previousaggregatesize/1024/1024" | bc )
+
+# Calculate difference in size between current and previous in both absolute and percentage terms
+aggregatesizediff=$((currentaggregatesize-previousaggregatesize))
+aggregatesizediffpc=$(echo "scale=5;$aggregatesizediff/$previousaggregatesize" | bc | awk '{printf "%.5f\n", $0}')
+
+# Calculate git log between the current and previous aggregation, by
+# -> First, calculate date/time of latest publication (epoch) in products repo
+# -> Next, calculate date/time of previous publication (epoch) in products repo
+# -> Finally, get a git log between those two dates (epoch) in data repo
+currenttagdate=$(git --work-tree=$repoproducts --git-dir=$repoproducts/.git log -1 $currenttag --format=%ct)
+previoustagdate=$(git --work-tree=$repoproducts --git-dir=$repoproducts/.git log -1 $previoustag --format=%ct)
+gitlog=$(git --work-tree=$repodata --git-dir=$repodata/.git log --format="%h %an %s" --after=$previoustagdate --before=$currenttagdate)
+gitlognumentries=$(git --work-tree=$repodata --git-dir=$repodata/.git log --format="%h %an %s" --after=$previoustagdate --before=$currenttagdate | wc -l | awk '{print $1}')
+
+# =====
+# = Now we're ready to output the message
+# =====
+
+# First part of the message is just a canned success message with a timestamp 
+msg="$(date) - Successfully published new UKf metadata.\n"
+
+# Second part is some stats about the UK fed
+msg+="-> The UK federation now has $membercount members and $entitycountuk entities.\n"
+
+# Third part is stats about the aggregate, and some diff info
+if [ $aggregatesizediff -lt 0 ]; then
+    aggregatesizediffnegated=$(( $aggregatesizediff * -1 ))
+    msg+="-> The main aggregate contains $entitycounttotal entities and is $currentaggregatesizemb MB ($aggregatesizediffnegated bytes smaller than the last publication, a $aggregatesizediffpc % difference).\n"
+elif [ $aggregatesizediff -eq 0 ]; then
+    msg+="-> The main aggregate contains $entitycounttotal entities and is $currentaggregatesizemb MB (exactly the same size as the last publication).\n"
+else
+    msg+="-> The main aggregate contains $entitycounttotal entities and is $currentaggregatesizemb MB ($aggregatesizediff bytes bigger than the last publication, a $aggregatesizediffpc % difference).\n"
+fi
+
+# Finally all commits
+if [ $gitlognumentries -eq 0 ]; then
+    msg+="There have been no commits since last publication; all changes are from imported entities only.\n"
+elif [ $gitlognumentries -eq 1  ]; then
+    msg+="There has been $gitlognumentries commit since the last publication:\n"
+    msg+="\`\`\`$gitlog\`\`\`"
+else
+    msg+="There have been $gitlognumentries commits since the last publication:\n"
+    msg+="\`\`\`$gitlog\`\`\`"
+fi  
+
+echo -e "$msg"
+exit 0