'Carriage slewed across the platform'

POTTERS BAR, England (CNN) -- CNN's Graham Jones was at Potters Bar station moments after a passenger train left the rails and careered into the buildings. (Full story) Here is his report:

It's a scene of complete devastation. This is a modern station with four platforms and much of it is destroyed.

One carriage has slewed across the platform and is wedged under the canopy. It must have hit it at some speed.

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Also, the bridge entering into the station where the rail lines go over one of the main roads in Potters Bar is a tangled mass of wreckage where presumably the train must have hit before careering across the platforms.

Bits of the bridge have sheered off and fallen onto two cars. One piece has smashed onto the roof of a car and mangled bits of steel are littering the road.

There is just one bogie, presumably from the rear carriage with four wheels, that has sheered off completely and is wedged into the station platform.

There are scores of emergency workers -- police, firefighters and ambulance staff -- on the scene and a police helicopter flying overhead.

I have talked to several people who witnessed the crash and they are very upset and in complete shock.

Potters Bar is on a mainline serving the capital and is one of the major outer London hubs used by a lot of commuters.