Little Grebe (Tachybaptus ruficollis) also known as the 'Dabchick'. Our smallest grebe with a very dumpy body, short neck, a tiny straight bill and in breeding plumage the yellow gape spot is usually visible at some distance. In all plumages they ususally display a distinctive 'powder-puff' rear end but this adult decided to show me more than I bargained for! FAB.
Taken at Barnes WWT - ISO 200; F/10; 1/400 @ 260mm and cropped.