The 140mph trains are expected to be introduced in 2009

New trains are to run from Kent on the Channel Tunnel rail link to a new Eurostar terminus at St Pancras station in central London.

The new 140mph trains, which represent an estimated £200m investment, will also support London's 2012 Olympic bid.

The trains are expected to be built by Japanese bullet train manufacturer Hitachi and introduced in 2009.

Transport Secretary Alistair Darling named Hitachi as the preferred manufacturer for about 30 six-carriage trains.

'Flagship scheme'

He said: "The technology on these trains is cutting edge, which could reduce journey times between Ashford and central London by 40 minutes each way.

"This service will also be the flagship transport scheme to deliver people to and from the Olympic Games, should the UK bid be successful."

The trains will be capable of moving spectators from central London to the Olympic park in Stratford, east London, in less than eight minutes.

New routes are also expected to include Gravesend, the Medway towns, Sittingbourne, Folkestone, Canterbury and Ramsgate.

David Quarmby, of the Strategic Rail Authority, said: "Today's confirmation brings a new rolling stock supplier to the UK market, and passengers can expect a high level of reliability, comfort and speed from these trains."