Start from Weir Wood (Layhams Lane). 20 mile route takes about 1hr 40mins to ride.
80% off road trails, single track and paths.

Additional loop can be added from Jackass Lane up to Keston via some really good stairs.

The North Downs Way is a bit rubbish, so I started on it but then turned back and road across the Warlingham and into more bridle ways I knew.

Map of ride here: http://connect.garmin.com/activity/376012318