The new £50m London Overground extension between Dalston Junction and Highbury & Islington opened today, three months ahead of schedule.
Mayor of London, Boris Johnson, opened the new 2.1km link in a ceremony this morning.
The extension will form an integral link between the East London Line and the rest of the Overground network, meaning that it will be possible to travel all the way from Croydon to northwest London.
The opening of the service will also create a continuous orbital railway around the capital.
Although the official opening of the line took place this morning, limited train services began running on the route last week.
Previously, passengers wishing to continue their journey from Dalston Junction to Highbury and Islington had to walk 200 yards to Dalston Kingsland station. The new section of line will improve journey times for passengers by eliminating the need to change trains.
However, passengers wishing to continue their journey past Highbury and Islington will still need to change.
Mr Johnson 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. This relatively short stretch of track will link three sides of the city and mean people can scoot around the edges of the capital on fast, reliable rail connections without needing to head into central London.
“Our engineers have performed marvels to complete their work three months early and it will provide a crucial connection for people heading to the Olympic Park next year.”
Most of the £1bn modernised East London Line was opened in May 2010, but the spur connecting Dalston Junction was due to open in May 2011.
The opening marks the completion of phase one of the East London Line Extension project. Phase two of the project, due to open in time for the 2012 Olympics, will extend the line from Surrey Quays via Peckham and Battersea, to Clapham Junction.
Mike Brown, Managing Director of London Rail, said: “The London Overground network continues to grow and offer Londoners real alternatives to journeys requiring a trip through central London.”