No hint of a Kumlien’s Gull in this bird. This looks like a pure bred Thayer’s Gull. Wonder if it came from the west or east to reach Britain? You cannot question the identity of this bird. Everything is perfect. The combination of black iris, heavy bill, strong head streaking, relatively heavy build of the bird and classic wing tip pattern make this a text book, ‘type specimen’ example of Thayer’s Gull. Finally!!! Lots of birds by default labelled as Thayer’s on the Great Lakes and other areas on the periphery of the published range don’t look this good (it doesn’t mean those birds are not Thayer’s). This bird is a very solid and strong Thayer’s (Bruce Mactavish, Newfoundland)