LONDON'S shortest Tube line has reopened today after five months of upgrade works.

The Waterloo and City line, nicknamed "The Drain", ferries over 37,000 passengers a day between Waterloo and Bank, without any intermediate stops.

The service was due to resume on September 1, but work by maintenance firm Metronet overran. The company will be fined hundreds of thousands of pounds for the delay.

Workers replaced all the track along the 1.5-mile line and fitted new communication systems.

The five four-car trains, made in 1992, were refurbished with CCTV and London Underground's red, white and blue colours.

Metronet promised faster journey times, more passenger capacity and a more reliable service.

An LU spokesman said the upgrade was "a complex project... in one of the most constrained parts of the network, with delivery a few days behind schedule".

The project is part of Transport for London's (TfL) £10 billion five-year investment program.

"We look forward to a safer, more reliable and comfortable Waterloo and City line," said LU chief Tim O'Toole.