Bison Hill, Whipsnade, Beds. The southern end of Dunstable Downs, a chalky outcrop of the Chiltern Hills.
A steep west-facing escarpment. There is free parking at a National Trust car park.

Personal Sightings:

9 June 2013. Mostly overcast with brief periods of sun. Breezy. 1 Grizzled Skipper, 3 Dingy Skippers, 3 Green Hairstreaks, 1 Small Copper, 1 Brown Argus, 3 Common Blues, 11 Small Heaths.

16 May 2014. The sun glimmered between the clouds then disappeared by about 1.00 pm. Met a transect counter, so did not count every butterfly. C. 10 Dingy Skippers, 2 Grizzled Skippers, 4 Brimstones, at least 4 Orange Tips, c. 12 Green Hairstreaks, 2 Common Blues, 1 Peacock, 7 Dukes, 1 Small Heath.