I have 4 pictures of a Possible Yellow-Legged Gull.
The 1st and 2nd pics are of a 1st bird, which is comparable to some LBBGs and shows a lighter tone, is it just a Common Gull? In both photos I'm looking at the Gull directly and centrely in the middle.
I reckon I've got a stronger case with 3 and 4, which show slightly darker tones than BHGs but lighter than LBBGs. In picture 3 the Bird is on the very left, you can clearly compare with the darker LBBG. Picture 4 the Bird is in the middle, its larger than the other smaller Gulls and has a slightly darker back colour (But lighter than any LBBG should have).