THEY are the words that rail passengers in Hampshire have often used to describe their commuter trains - old, dirty and late.

But that will all change for the better with the opening of a £25m state-of-the-art maintenance depot in Southampton.

The Siemens depot - the most modern one of its kind in the UK - is now up and running after three years of preparation, providing jobs for 150 people.

Yesterday the facility at Northam, next to the Meridian TV studios, was officially unveiled amid a fireworks fanfare by transport millionaire Brian Souter, the head of Stagecoach, which owns South West Trains.

The 230-metre long covered depot, with hi-tech work stations along pristine-condition platforms, is being lauded as a benchmark in excellence.

A new "pit stop" style maintenance regime, with faulty trains back in service within hours instead of days, will reduce delays and cancellations for passengers on some of the busiest commuting routes into London.

The depot will provide round-the-clock service for the 785-car fleet of Siemens' new Desiro trains, the first of which will be in passenger service for the winter timetable change in September.

Siemens has a 20-year maintenance contract with SWT, which runs services between the south coast and London Waterloo, for the new fleet of electric trains.

They will replace the old slam-door trains - built in the 1950s and 1960s - that have been the scourge of commuter travel.

SWT managing director Andrew Haines told scores of VIP guests yesterday that the old trains were usually described as "old, dirty and late".

But he added: "All of those will be consigned to the bin." The sleek Desiro trains have undergone rigorous testing in Germany, including being tested on a track that replicates the British weather, such as ice and rain.

Reassuringly for passengers, the fleet has even been tested for leaves on the line.

Ironically, the official opening had to be delayed itself because of a heavy downpour.

Normal service resumed after 15 minutes.