A rail company has promised its electric trains are more reliable than ever now a £125 million depot is nearing completion.

Southern Railway is adding the finishing touches to Lovers Walk depot at Brighton train station following a fouryear reconstruction.

The work was needed to adapt the maintenance and storage facility to service the Electrostar trains, which began replacing slam-door vehicles in 2002.

At first the modern fleet had teething problems, which included malfunctioning toilets and air-conditioning systems. Now Southern says each vehicle will travel between 18,500 and 20,000 miles before suffering a technical problem that will cause a delay of more than five minutes.

The depot dates back to the 1850s and still has its original external structure.

Until the revamp it had been basically unchanged for about 50 years.

Depot manager Haydn Vaughan said: "It was a facility that had been around since the Forties and Fifties.

"It has become much more efficient."

Mr Vaughan admitted there had been problems at first with the hi-tech computer systems on the new trains.

He said: "These are two different generations of technology.

"The slam doors, technology-wise, dated back to the Thirties. There was not a lot that could go wrong. These trains had more technology in them that had an opportunity to go wrong."

The last slam-door train stopped running by the end of last year and the disused carriages were scrapped or sold to railway preservation societies.

The 134 new trains are maintained in Brighton and Selhurst. Each vehicle returns to the depot for planned servicing every 40 to 45 days, when it is cleaned thoroughly and the toilets are emptied.

The trains travel 15,000 miles every five to six weeks.

Unlike their predecessors, they have air conditioning, sand boxes which grit the track ahead of the wheels for braking in bad weather, wi-fi internet access on some services and toilets with storage tanks.

On the older trains, when a passenger flushed the toilet the entire contents would be strewn out on the track, wherever the train was at the time. The only ventilation was to open the window.

The new trains build speed quicker so it is possible to make up time more easily if a train is running late.

Chris Burchell, managing director of Southern, said: "They are more reliable than the old ones. One driver said it was like going from a Morris Minor to a Mercedes. We are on the verge of hitting 90 per cent of trains being on time over the last year, compared with a base of the mid- 70s three years ago. Our customer satisfaction has gone up to 80 per cent from 67 per cent."

Driver Sean Jones, from Southwick, said the new vehicles were more reliable and comfortable for passengers.

He said: "There were teething problems.

They are much more reliable now. The old trains were breaking down and it was affecting the service."