Photo taken on 26/04/08 at Studham, Beds., on Walk 2 of the Chiltern Chain Walk
There are actually numerous varieties of this very common wildflower. It's name comes from the French for "Lion's Teeth", because of the shape of the leaves.
Photo taken on 24/04/09, near Aston Clinton,, Bucks.
Photo taken on 3/05/08 near Wigginton, Herts., on Walk 2 of the Chiltern Chain Walk