A guided tour round the Greater London boundary

A guided tour of the Greater London boundary (clockwise) Hillingdon Welcome to Heathrow but the side most passengers never see, the cargo-loading logistics backside. Past massive secure sheds trading whatever, first on the local Bedfont Road then switching to the more circuitous Southern Perimeter Road. Two rivers run parallel for a mile and a half, the Longford and the Duke of Northumberland's, each shamelessly shifted out of the way by airport construction. Walk along or walk between, perhaps pausing for refreshment at The Rising Sun or Esso garage, as global jet engines scream alongside. These roads aren't made for pedestrians - if not aiming for Spout Lane why would you even be here? The Poyle Interchange includes the westernmost point in Greater London, then it's time to follow the M25's clockwise carriageway as far as the M4 stack interchange. The Bigley Ditch threads through in tiny meanders, first the river's former course and then the unengineered original, at least until a…