In Lincolnshire, Britain
V. nice morning outing with Roy (Orbison) Twigg, Mark Reeder and Ray the Voice. Arrived at just the right moment to drop onto good views of a stunning looking, rather dark juvenile Thayer’s Gull. As we were leaving a little later it appeared even closer giving excellent ‘scope filling and fine flight views. I heard the word ‘classic’ banded around a little. I think dark end of the spectrum is probably more accurate. Certainly is stunning but maybe in the darker 20% or even less of Thayer’s Gulls in this plumage. Just looks more striking than paler birds.
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If you want a bit more on recent Thayer’s types in Britain and Ireland. Fill yer boots:
juveniles from breeding grounds
juvenile nr Enniskillen, N. Ireland
a juvenile Thayer’s-like bird in co. Clare
Birding Frontiers 
Hi Martin. (I wrongly put this comment on the Enniskillen bird page)
You have probably seen this one.
http://www.talk.gull-research.org/viewtopic.php?f=13&t=753
JanJ
hi Jan
Thanks for this. I have already responded to Kent following an email from him. In it I said I felt the bird was not a Thayer’s Gull on what I could see (and on quick gut reaction) and I felt his first assessment was probably right: some kind of ‘Viking Gull’. However, I see that since then there have been some strong arguments in favour of Thayer’s though I still think there are problems with with jizz/structure and plumage that cause me to struggle with the idea of it definitely being a Thayer’s.
Martin