diff --git a/code/sudo-mode/MemberRelationsPageExtension.php b/code/sudo-mode/MemberRelationsPageExtension.php
new file mode 100644
index 0000000..3a576eb
--- /dev/null
+++ b/code/sudo-mode/MemberRelationsPageExtension.php
@@ -0,0 +1,57 @@
+<?php
+
+namespace SilverStripe\FrameworkTest\SudoMode;
+
+use RuntimeException;
+use SilverStripe\Forms\Form;
+use SilverStripe\Core\Extension;
+use SilverStripe\Security\Member;
+use SilverStripe\Forms\GridField\GridField;
+use SilverStripe\Forms\GridField\GridFieldConfig_RecordEditor;
+use SilverStripe\ORM\ArrayList;
+
+/**
+ * Extension that adds Member relations on a page to test that sudo-mode
+ * works on gridfields for relations
+ *
+ * @extends Extension<Form>
+ */
+class MemberRelationsPageExtension extends Extension
+{
+    private static $has_many = [
+        'HasManyMembers' => Member::class
+    ];
+
+    private static $many_many = [
+        'ManyManyMembers' => Member::class
+    ];
+
+    public function updateCMSFields(&$fields)
+    {
+        $gridField = new GridField('HasManyMembers', 'HasManyMembers', $this->owner->HasManyMembers());
+        $config = GridFieldConfig_RecordEditor::create();
+        $gridField->setConfig($config);
+        $fields->insertAfter('Title', $gridField);
+        // Intentionally using an ArrayList here to check that the gridfield can handle it
+        $list = new ArrayList($this->owner->ManyManyMembers()->toArray());
+        $gridField = new GridField('ManyManyMembers', 'ManyManyMembers', $list);
+        $config = GridFieldConfig_RecordEditor::create();
+        $gridField->setConfig($config);
+        $fields->insertAfter('Title', $gridField);
+        return $fields;
+    }
+
+    protected function onBeforeWrite()
+    {
+        $member = Member::get()->first();
+        if (!$member) {
+            throw new RuntimeException('No Member record found, create one in your test setup');
+        }
+        if ($this->owner->HasManyMembers()->count() === 0) {
+            $this->owner->HasManyMembers()->add($member);
+        }
+        if ($this->owner->ManyManyMembers()->count() === 0) {
+            $this->owner->ManyManyMembers()->add($member);
+        }
+    }
+}