diff --git a/lib/deprecatedlib.php b/lib/deprecatedlib.php
index 16e4abe1c70..f94c5c7d69e 100644
--- a/lib/deprecatedlib.php
+++ b/lib/deprecatedlib.php
@@ -3231,6 +3231,13 @@ function message_count_unread_messages() {
     throw new coding_exception('message_count_unread_messages has been removed.');
 }
 
+/**
+ * @deprecated since 3.10
+ */
+function serialise_tool_proxy() {
+    throw new coding_exception('serialise_tool_proxy has been removed.');
+}
+
 /**
  * Checks if current user is shown any extra fields when listing users.
  *
diff --git a/mod/lti/locallib.php b/mod/lti/locallib.php
index 1ced06aeea0..065d2243f92 100644
--- a/mod/lti/locallib.php
+++ b/mod/lti/locallib.php
@@ -4291,39 +4291,6 @@ function serialise_tool_type(stdClass $type) {
     );
 }
 
-/**
- * Serialises this tool proxy.
- *
- * @param stdClass $proxy The tool proxy
- *
- * @deprecated since Moodle 3.10
- * @todo This will be finally removed for Moodle 4.2 as part of MDL-69976.
- * @return array An array of values representing this type
- */
-function serialise_tool_proxy(stdClass $proxy) {
-    $deprecatedtext = __FUNCTION__ . '() is deprecated. Please remove all references to this method.';
-    debugging($deprecatedtext, DEBUG_DEVELOPER);
-
-    return array(
-        'id' => $proxy->id,
-        'name' => $proxy->name,
-        'description' => get_string('activatetoadddescription', 'mod_lti'),
-        'urls' => get_tool_proxy_urls($proxy),
-        'state' => array(
-            'text' => get_string('pending', 'mod_lti'),
-            'pending' => true,
-            'configured' => false,
-            'rejected' => false,
-            'unknown' => false
-        ),
-        'hascapabilitygroups' => true,
-        'capabilitygroups' => array(),
-        'courseid' => 0,
-        'instanceids' => array(),
-        'instancecount' => 0
-    );
-}
-
 /**
  * Loads the cartridge information into the tool type, if the launch url is for a cartridge file
  *
diff --git a/mod/lti/upgrade.txt b/mod/lti/upgrade.txt
index 2c330ca6def..dfef7d68b37 100644
--- a/mod/lti/upgrade.txt
+++ b/mod/lti/upgrade.txt
@@ -4,6 +4,7 @@ This files describes API changes in the lti code.
 
 * get_jwt_claim_mappings() function has been added to service_base class. It allows a service subplugin to be
   compatible with LTI 1.3 by exposing its 1.1 custom parameters to LTI 1.3 claim mapping.
+* The `serialise_tool_proxy` method, deprecated since 3.10, has been removed and can no longer be used
 
 === 4.1 ===