diff --git a/app/models/user.py b/app/models/user.py
index 831465ec7..b5888e9c8 100644
--- a/app/models/user.py
+++ b/app/models/user.py
@@ -652,6 +652,12 @@ class Users(ModelList):
         for user in self:
             if user.id == id:
                 return user.name
+        # The user may not exist in the list of users for this service if they are
+        # a platform admin or if they have since left the team. In this case, we fall
+        # back to getting the user from the API (or Redis if it is in the cache)
+        user = User.from_id(id)
+        if user and user.name:
+            return user.name
         return 'Unknown'
 
 
diff --git a/tests/app/main/views/test_history.py b/tests/app/main/views/test_history.py
index f25898f39..2904d9db3 100644
--- a/tests/app/main/views/test_history.py
+++ b/tests/app/main/views/test_history.py
@@ -36,7 +36,7 @@ from tests.conftest import SERVICE_ONE_ID, normalize_spaces
                 'Created an API key called ‘Good key’ '
                 'Test User 10:09am '
                 'Created an API key called ‘Key event returned in non-chronological order’ '
-                'Unknown 2:01am '
+                'Test User 2:01am '
                 'Created this service and called it ‘Example service’'
             ),
         ),
@@ -79,7 +79,7 @@ from tests.conftest import SERVICE_ONE_ID, normalize_spaces
         (
             '10 October 2010',
             (
-                'Unknown 2:01am '
+                'Test User 2:01am '
                 'Created this service and called it ‘Example service’'
             ),
         ),