Intent on joining the fishing action

Met this big bird down by the water’s edge today. Much bigger than any of the number of seagulls who were hovering over the water at Eling Creek, just off the northern reaches of Southampton Water.

This one was taking a close interest in a number of families who were crabbing from the quay wall just a few feet from the craft on which it settled itself, and indeed what they were catching in the relatively shallow water, while kept chattering away with a high pitched squawk all the time I was there.

But what was it? Can any Blip follower identify it for me?