Yellow-legged Gull?

Yesterday morning I went, once again, to Eske/Pulfin Fen. It was very bright, but a light northerly breeze was pretty chilly. The walk was a tale of two halves really, with the first half (the walk up) being virtually birdless, almost no ducks on the lake and only two Fieldfares were of any interest. Beyond the lake 33 Mute Swans were feeding in a field, but no Whooper Swans today.

On the way back (second half), suddenly the lake was filled with ducks and Geese. The regular 200 or so Greylags all landed in the lake as I watched and 2 Canada Geese were sitting on the island, strangely, this species doesn't turn up here often at all. Amongst the ducks were about 30 Tufted Duck, 10 Pochard, 150 Wigeon, 6 Teal, 50-60 Mallard, 2 Gadwall and 4 Goldeneye, including one male displaying which was the highlight until I noticed 3 large Gulls.

Two of these were adults, and appeared to be Herring Gulls, but perhaps slightly darker than normal. When they eventually flew, the black wing markings suggested argentatus, but I couldn't be sure as I was focussing my attention on the single first winter gull that was present. This bird immediately struck me as different to an immature Herring Gull, in fact I thought it was a Yellow-legged Gull straight away - not that frequently recorded up here. It was exceptionally white in appearance with just a little dark smudging around the eye. Its bill was noticeably longer than the other two birds' bills and heavier too. The bill was dark black with just a hint of pale colouration at the base. The bird's head was fairly long and sloping and its wings were pale grey with distinct dark markings - no smudginess at all. The tertials were completely dark, but I couldn't make out any pale edges. The primaries were long and black. In flight it had a clear white back with no flecking and a distinct black band at the end of the tail. The bird's chest and belly were very pale with some spotting. In flight the colouration of the wings confirmed that it was a first winter bird and the wing tips were contrastingly dark compared to the rest. More than that I didn't notice,

Since seeing this gull I have discovered that I missed a few key features. Unfortunately I'm not that good! However, I have seen plenty of Yellow-legged Gulls and the jizz of this bird seemed right.

If any gull experts want to comment on this fairly poor description, please feel free to.

On the way back 2 Tree Sparrows flew out of some bushes and 2 male Reed Buntings looked like they were in a dispute over a female.