The first South West Trains Desiro UK train arrives at a mock-up of Clapham Junction station at Siemens' test track in Wildenrath, Germany 

The UKs biggest train order for £1 billion was signed exactly a year ago and today the first South West Trains Desiro UK train is unveiled.

The train, a Class 450, is being rolled out at Siemens test track at Wildenrath in Germany - the first of 785 new carriages that will replace South West Trains Mark I slam-door fleet.

The new trains will bring significant benefits to the travelling public including: air conditioning, automatic sliding doors, audio and visual passenger information displays and dedicated facilities for disabled passengers.

They will also be safer, with the addition of a crumple-zone similar to that found on motor cars - a first for the UK.