Yellow-legged Gull

Yellow-legged Gull, Landbeach, 11th October 2008, © Dick Newell
This gull has a very large mirror on P10 merged into the white tip on that feather. It also has a mirror on P9. The black band on P5 is a bit greyed out on the inner web and is not continuous across the feather, it is split in the middle. The pattern of P9 and P10 as well as the lack of a mark on P4 seems to fit what Olsen & Larsson say about eastern populations of Yellow-legged Gull. Or is it just an unusual western Mediterranean bird?