I would like to use your expertise on this gull (two attached pictures).
I have taken these two pictures in Stockholm today. The pro caspian gull features are the small dark eye and the dark line on the bill despite the fact that the rest of the plumage indicate an adult. The bad points are the quite big gonydeal angle and the not so long bill.
Unfortunately it never spread its wing during my observation so I can say nothing on the P5 or on possible black tongue.
Do you think that this is just an Herring gull ssp argentatus or could it be a Caspian?