There are quite a lot of black-headed gulls in the photo above. They don't have a black head in the winter, just a smudgy neck marking. When I took the picture they were transitional.
Between the lake and the car park is a crash barrier and the gulls like to perch on it. If scared they all, obviously, fly around a bit and then slowly come back in to land.
The metal bar at the top of the barrier is wider than their talons can grip easily and slippery when wet. They have to employ a fair bit of balancing and flapping to come to rest on it.
What I noticed is that, once a few have perched and got a grip, there is an easier way to land. You simply aim for the middle of the back of an already-perched bird, knock it to the floor and take its place. Hilarious, especially the dethroned who then peck around the grass a bit with an 'I meant that, you know' attitude. Who likes to own up to being bullied?