Photo taken 27/06/10 at College Lake, Bucks.
Apologies for the very slightly out of focus photo! Knotted Hedge-Parsley grows mainly by the seaside, on grassy banks, but in the east of England it is also found on arable land. It flowers between May and July.
This is a slight 'cheat' as the photo was taken at one of the meadows at the College Lake reserve where such wildflowers are deliberately planted and grown. I have not yet come across it on any of my walks.