Lesser Black Backed Gull.

I'm not sure but I think that this may be a gull in its second winter plumage hence the dappled markings. I saw another gull which I think is a Great Black Backed Gull, it's legs are not yellow. I am waiting for a friend/ornithologist  to come back to me on that so am putting it in my extra photos. The GBBG is not commonly seen in Bushy Park. I will correct my mistake if I find out that I am incorrect!
PS My extra is indeed a GBBG.