Great Black-backed gull

I think this is a Great Black-backed gull Larus marinus, but I could be wrong.
Mr U&L and I went to Shoreham today for a walk along the shingle beach which at this time of year is alive with colourful plants (see extra one). It was amazing, and the European wall lizards that live in the walls of the fort and the houses that back onto the beach were out in good numbers (see extra 2). as was the starry clover (see extra 3) But my photograph of the day was this wonderful Great Black-backed gull.