Double the number of trains will now be running from Clapham to Stratford following the completion of a three-year £550m upgrade.

Transport for London (TfL) described the upgrade as an early Olympic transport legacy for Londoners ahead of the 2012 games.

Two trains an hour will travel direct from Clapham Junction to Stratford, taking just over an hour, while two involve a four-minute transfer at Willesden Junction.

The new timetable is the result of the first major revamp of the London Overground since 1869, which has seen TfL fund 57 new air-conditioned trains, and a station refurbishment programme to deliver cleaner and well-staffed stations along the route.

Mike Brown, managing director of TfL’s rail division, said: “The new timetable provides the high frequency, highly reliable, air conditioned service TfL promised when it took over the railway.“ The Mayor of London Boris Johnson, said: “It will be immensely popular with 2012 Games goers but will be of benefit to Londoners for many years beyond the Olympics.”

Richard Tracey, London Assembly member for Merton and Wandsworth, said: “This is more good news for Battersea and Clapham Junction from the Mayor, GLA, and TfL about the London Overground and Olympic travel options next year. Our constant campaigning messages from Wandsworth are continuing to pay great dividends."