The Jubilee line has reopened today, two days ahead of schedule, after work to add a seventh carriage to each train.

The line, which carries more than 400,000 passengers on a weekday, was due to be shut for five days from Boxing Day until tomorrow.

But a reduced service has already started at around 10.30am, with 22 trains running every six to eight minutes. A full service will resume on January 8, as planned before.

The longer trains will boost peak-time passenger capacity by 17%, from 33,000 people an hour to 39,000.

Four new trains were also added, increasing the fleet from 59 to 63.

'Extra Christmas present'

The closure was unavoidable, but was planned when the Tube is most lightly used, said George McInulty, Jubilee line director. "Six and seven-carriage trains cannot be run at the same time."

More than 550 people worked around the clock over Christmas to test the extended trains and signalling, adjust platform edge doors and realign CCTV cameras.

Preparation to accommodate the longer trains at depots has been done in advance.

Mr McInulty called the line's early reopening a "wonderful extra Christmas present" for commuters.

A replacement bus service will continue to run today and tomorrow, while Neasden station remains closed for refurbishment.

The project is part of Transport for London's £10 billion five-year investment programme to improve the capital's transport network.