Photo taken 11/05/09 on Watlington Hill, Oxon.
I think I first saw this on Lodge Hill near Bledlow on Day 4 of my Berks-Essex Walk, and I have seen it quite often in the Chilterns since then. As well as on chalk lands, it also grows on mountains and I saw it almost everywhere I walked in the Lake District in May 2007. It flowers from May to August.
Photo taken 26/05/07 on Swyncombe Down on Day 21 of my second Chiltern Way walk