diff --git a/app/schemas.py b/app/schemas.py
index 6de8c5ed4..7cad5de42 100644
--- a/app/schemas.py
+++ b/app/schemas.py
@@ -292,11 +292,24 @@ class NotificationWithTemplateSchema(BaseSchema):
 
 
 class NotificationWithPersonalisationSchema(NotificationWithTemplateSchema):
-    template = None
     actual_template = fields.Nested(TemplateHistorySchema,
                                     only=['id', 'name', 'template_type', 'content', 'subject', 'version'],
                                     dump_only=True)
 
+    class Meta(NotificationWithTemplateSchema.Meta):
+        # mark as many fields as possible as required since this is a public api.
+        # WARNING: Does _not_ reference fields computed in handle_template_merge, such as
+        # 'body', 'subject' [for emails], and 'content_char_count'
+        fields = (
+            # db rows
+            'id', 'to', 'job_row_number', 'template_version', 'billable_units', 'notification_type', 'created_at',
+            'sent_at', 'sent_by', 'updated_at', 'status', 'reference',
+            # computed fields
+            'personalisation',
+            # relationships
+            'service', 'job', 'api_key', 'actual_template'
+        )
+
     @pre_dump
     def handle_personalisation_property(self, in_data):
         self.personalisation = in_data.personalisation
@@ -312,8 +325,13 @@ class NotificationWithPersonalisationSchema(NotificationWithTemplateSchema):
             renderer=PassThrough()
         )
         in_data['body'] = template.replaced
-        if in_data['template']['template_type'] == 'email':
+        template_type = in_data['template']['template_type']
+        if template_type == 'email':
             in_data['subject'] = template.replaced_subject
+            in_data['content_char_count'] = None
+        else:
+            in_data['content_char_count'] = len(in_data['body'])
+
         in_data.pop('personalisation', None)
         in_data['template'].pop('content', None)
         in_data['template'].pop('subject', None)
@@ -532,7 +550,6 @@ job_email_template_notification_schema = JobEmailTemplateNotificationSchema()
 notification_schema = NotificationModelSchema()
 notification_with_template_schema = NotificationWithTemplateSchema()
 notification_with_personalisation_schema = NotificationWithPersonalisationSchema()
-notification_with_personalisation_schema_load_json = NotificationWithPersonalisationSchema(load_json=True)
 invited_user_schema = InvitedUserSchema()
 permission_schema = PermissionSchema()
 email_data_request_schema = EmailDataSchema()
diff --git a/tests/app/notifications/test_rest.py b/tests/app/notifications/test_rest.py
index 3386f1d84..df611adca 100644
--- a/tests/app/notifications/test_rest.py
+++ b/tests/app/notifications/test_rest.py
@@ -564,6 +564,7 @@ def test_get_notification_by_id_returns_merged_template_content(notify_db,
             assert response.status_code == 200
             assert notification['body'] == 'Hello world\nYour thing is due soon'
             assert 'subject' not in notification
+            assert notification['content_char_count'] == 34
 
 
 def test_get_notification_by_id_returns_merged_template_content_for_email(
@@ -587,6 +588,7 @@ def test_get_notification_by_id_returns_merged_template_content_for_email(
         assert response.status_code == 200
         assert notification['body'] == 'Hello world\nThis is an email from GOV.UK'
         assert notification['subject'] == 'world'
+        assert notification['content_char_count'] is None
 
 
 def test_get_notifications_for_service_returns_merged_template_content(notify_api,
@@ -623,6 +625,44 @@ def test_get_notifications_for_service_returns_merged_template_content(notify_ap
             }
 
 
+def test_get_notification_public_api_format_is_not_changed(notify_api, sample_notification):
+    with notify_api.test_request_context(), notify_api.test_client() as client:
+        auth_header = create_authorization_header(service_id=sample_notification.service_id)
+
+        response = client.get(
+            '/notifications/{}'.format(sample_notification.id),
+            headers=[auth_header])
+
+        assert response.status_code == 200
+        notification = json.loads(response.get_data(as_text=True))['data']['notification']
+        # you should never remove things from this list!
+        assert set(notification.keys()) == {
+            # straight from db
+            'id',
+            'to',
+            'job_row_number',
+            'template_version',
+            'billable_units',
+            'notification_type',
+            'created_at',
+            'sent_at',
+            'sent_by',
+            'updated_at',
+            'status',
+            'reference',
+
+            # relationships
+            'template',
+            'service',
+            'job',
+            'api_key',
+
+            # other
+            'body',
+            'content_char_count'
+        }
+
+
 def test_get_notification_selects_correct_template_for_personalisation(notify_api,
                                                                        notify_db,
                                                                        notify_db_session,