I saw this big, snowy white bird – a Little egret – as it flew over and I legged it round the corner to where it had landed in the margins of a small shallow lake. It only stayed there for about a minute before flying away, but I got a couple of good photos from afar as it stalked briefly through amongst the plants.
Its long black legs are mostly hidden in the water, as are its bright yellow feet. You also can't see any evidence of the typical long slender plume on the back of its head. Overall it's most similar to a Heron, but smaller and pure white and hard to mistake even in flight.
These birds are most numerous around the South and East coast, though it's still relatively rare (but increasing rapidly – mostly as a winter migrant) so I was fairly lucky to see this one 40 miles from the coast in Hertfordshire.