Peewit!

That's what they say!

It has lots of other names too - the Northern Lapwing or Green Plover (Vanellus vanillas).

It is a common wader found on marshes and estuaries, but likes to breed on open farmland. This was one of many that are in residence at the Barn Elms WWT under the Heathrow flight path.

They have been in a bit of decline in the UK, probably due to modern intensive farming methods. But they seem to thrive where the conditions are right for them.