Scope views of the pit are pretty good at present but both yesterday and today have been very warm, with an abundance of heat haze making photography difficult. It's a stretch for my 400mm lens to produce anything decent at the best of times here and so the efforts below are really just for documentation. Unfortunately the near-adult wasn't photographed despite doing a brilliant fly-past at about 30m range - I should have nailed it but my camera was on the wrong settings and so all I have are blurs.
Bird #1: juvenile, 17-18 August
I'm a bit sceptical about whether this is a pure Caspian Gull. Plumage is a little on the dark side - not out of range for a juvenile Casp but, when combined with the fairly Herring-like structure (quite big-headed and short-billed) plus quite heavily marked uppertail and undertail coverts, alarm bells sound. However it possesses the typical mouse-brown basal colour as well as the long, drooping lower tertials of a juvenile Casp and does kind of just look like one - if you don't stare too hard! The underwing is pretty pale, too, if not as pale as it can be in cachinnans. Perhaps it's from Germany.
Bird #2: juvenile, 18 August
Unlike the other youngster, no doubt about this one! First shot is with the DSLR, second with my iPhone 5.
Bird #3: 3cy (2s/3w), 17 August
Structurally quite obvious and also showed a small white mirror on retained p10.
Bird #4: 3cy(?), 17-18 August
At least eight Yellow-legged Gulls were seen over the two sessions with the commonest age class being juveniles (four) followed by 2cy (three) and a single 4cy. Weirdly no adults; traditionally I've found them to be the commonest age class here in past summers.
Juvenile Yellow-legged Gull, 17 August