For 140 miles, the London LOOP (London Outer Orbital Path) follows a green corridor right around the capital, offering a circular walk among secret countryside that can make you forget you're within a few miles of Heathrow Airport, the A13, or the suburban sprawl of Croydon, Watford or Dagenham. Here is rolling downland near Coulsdon, the forest of Enfield Chase, the lonely Thames marshes at Rainham, the classical parkland of Bushy Park and a canalside stroll at Uxbridge. London could not seem further away. Each of the guide's 15 sections represents a day's walk of reasonable length, and starts and finishes at a public transport point.