Yellow-legged Gull is an increasingly common summer visitor to London and the south-east, and I've now seen quite a few in Wanstead, which I realise is rather elitist of me. If you had to order the commoner large gulls in adult plumage in terms of increasing darkness, Herring Gull would be at the lightest end of the scale at light grey, with Lesser Black-backed Gull in the middle with a charcoal-grey mantle, and Great Black-backed Gull approaching dense actual black, as well as being an order of magnitude larger. Yellow-legged Gull sits between Herring and Lesser Black-backed - a darker grey that is nonetheless a long way from charcoal. Herring Gull has pink legs, LBB has yellow legs, and these are the only two real confusion species unless we throw Caspian into the mix. Generally though people try and turn other gulls into Caspians, rather than the other way around. Anyway, enough boring ID stuff. If you want to see one in Wanstead, we have one! Early mornings the bird below is currently favouring the playing fields adjacent to the two tower blocks at the extreme western end of the Flats. There are generally some LBBs there as well so that you can accurately judge colour.