The Hillingdon Trail hidden is a London based walk through woods, fields, meadows, parks and open spaces including Ickenham Marshes, Gutteridge and Ruislip woods a National Nature Reserve all dotted around the suburbs houses and towns of Hillingdon. The route runs from Harefield in the North to Cranford in the South and meets the Grand Union Canal for the last 5km.  https://www.hillingdon.gov.uk/article/4888/Hillingdon-Trail