Photo taken on 9/06/07 near Aldbury, Herts., on Day 25 of my second Chiltern Way walk.
I first saw this near Tom's Hill and Aldbury in Hertfordshire, where it covers the floor of a large part of the woodland. I have subsequently seen it near Markyate on one of my local walks. It is not a native species, but was introduced from East Asia. It flowers from July to October (so the photo above was taken well before it was at its best).
Photo taken on 8/07/08 near Markyate, Herts.