Commuters will be able to travel across the city on the London Overground earlier than expected after work on a new link finished three months early.

Passengers can now travel more swiftly between Richmond station and north London, the City and the south of the capital, after the 2.1km link was opened between Highbury and Islington station and Dalston Junction by London Mayor Boris Johnson yesterday.

He said: “We are piecing together a rail version of the M25 in the capital, an orbital rail link that is making it vastly easier for millions of Londoners to whizz from one side of the city to another.”

A multi-million pound upgrade of the London Overground has been carried out on the line and is expected to be completed in May, following the recent instalment of signalling equipment.

The new signals will allow up to eight trains an hour to run during peak time on the line, which runs from Stratford to Richmond or Clapham Junction - double the current number.

It will allow Richmond residents to travel to the site of Olympic Games with ease in 2012.

Andrew Munden, Network Rail route director, said: "London relies on rail to get more than a million people to and from work every day, which is why investment in projects like the London Overground upgrade is so important to the capital's economy.”