Rail operator South Central has ordered 700 new trains to replace ageing slam-door coaches on its Sussex routes.

The order - worth about £850 million - has been placed by Govia on its South Central franchise, which includes the London to Brighton line.

The existing slam-door rolling stock is among the oldest running on the railways.

Govia took over the franchise last year when French company Connex lost its licence.

The order has been placed with Canadian transport company Bombardier.

Govia chief executive Keith Ludeman said: "The order demonstrates our desire to get on with the job of improving South Central as quickly as we can.

"We aim to replace approximately 600 Mark 1 slam-door carriages by December 2004. We were also anxious to resolve the worst aspects of the overcrowding problem on South Central routes as quickly as possible."

The new trains will be capable of speeds up to 100mph where line speeds allow.

The order involves 28 three-carriage trains and 154 four-carriage trains.

It is hoped the first will be delivered to South Central during this summer with completion due by November 2004.

The air-conditioned, four-car trains can accommodate 266 passengers. There are toilets for disabled people and space for wheelchairs and cycles.