If you are considering walking this route yourself, please see my disclaimer. You may also like to see these notes about the maps and GPX files.
Google map of the walk (this route uses Alternative 1 on the Google map)
The bridleway immediately passed a bungalow on the right, and continued for several hundred yards between old hedgerows either side. It eventually emerged onto the top of Bison Hill, where I followed a path going half-right through the grass. At a fork in the path I went left, descending slightly with a car park (closed) to my left. At a path crossroads in the grass I turned right to reach a metal kissing-gate (another path was a short way to my left, close to a road), through which a path continued with the hillside soon sloping down to my left. I soon reached a very faint fork where I kept right (the almost imperceptible path forking left was the way I always used to go here, but the last time I went that way in 205 it was overgrown and blocked by thorny bushes). After a couple of hundred yards or so there was a short descent that brought me to a crossroads of sunken tracks worn into the hillside - these are old drovers' ways i.e. paths shepherds used for centuries to move their sheep from place to place.
The start of the bridleway to Bison Hill
The bridleway to Bison Hill
The bridleway to Bison Hill
Arriving at Bison Hill
Path on Bison Hill, heading to the metal kissing-gate
Path on Bison Hill
I went straight on here, dropping more steeply downhill. I slowed right down and spent the next 20 minutes or so going very slowly as I was now looking for butterflies - I've included a few photos of what I found. At the bottom of the slope I followed the path as it curved right. Soon the path was again a sunken track with an embankment on my left, gradually working its way back up the hillside.
The old Drovers' Way descending Bison Hill
The old Drovers' Way descending Bison Hill
The old Drovers' Way descending Bison Hill
The path reaching the foot of Bison Hill
The old Drovers' Way slowly ascending Whipsnade Downs
The old Drovers' Way slowly ascending Whipsnade Downs
The old Drovers' Way slowly ascending Whipsnade Downs