Any question answered...

Can anyone tell me what the black box shape thing is on the top left of this map?

http://www.flashearth.com/?lat=52.634207&lon=0.924703&z=16.8&r=0&src=msl

I thought it was the old fuel dump at first

But then this picture shows nothing in exactly the same spot;

http://goo.gl/maps/V5dH

Maybe settling pond for animal poo? Any fairly large cattle/pig/chicken operations nearby?