The Chilterns Cycleway is a meandering 275km loop around the Chiltern Hills. This route sets out from Regent's Park, and heads north-west to sample a 50km section of the trail.
Leaving London just south of Watford, you'll pass Chalfont village and be into the Hills. From there, follow the undulating backroads via Latimer and Ashley Green to Aldbury, where Musette Café serves crispy pizza from 12 till 3pm.
After a refuel, tackle Tom's Hill - just shy of a kilometre long with an average gradient of 7%. Something to get the blood flowing again. The route then reaches its most northerly point before turning homewards. You can easily bail out for a train at St Albans if you've had enough.