Passengers today told of their terror aboard a runaway train which crashed into another at a station.

Moments before the impact they were warned to brace themselves and hold on to small children.

The Cardiff to Brighton train was being shunted into Chichester station last night after breaking down just up the line.

But it broke loose and rolled on, ploughing into a waiting train at the platform at low speed.

Paramedics and police raced to the scene to give first aid and four people were taken to St Richard's Hospital in Chichester with minor injuries.

Simon Gumbrell, 34, an electronics engineer from Shoreham, was at the front of the Brighton-bound train when it crashed at just after 6pm.

He was treated in hospital for whiplash injuries.

Mr Gumbrell, who uses the Wessex Trains service to travel to visit his seven-and-a-half month old daughter Chloe in Wales, said: "We broke down just outside Chichester.

"A train pushed us down the track the wrong way. Then a train came from behind and started to shunt us to the station.

"It was very frightening because just before the crash a female member of staff came through the carriage and told us to gather up any small children and prepare for a small impact.

"Seconds later we hit the other train and it was more than a small impact. We all got jolted forward, which is when I hurt my neck.

"Everyone was pretty scared. The Wessex Trains staff did not seem to know what was going on. There was chaos. A lot of people were very upset and frightened.

"When the train slammed into the back people were thrown forward in their seats. We were thrown about again when we hit the train in the station."

A spokesman for Wessex Trains said: "Our train had failed in the Chichester area. It was undergoing a manoeuvre with another train when the two trains became separated. At this stage we do not know why. They were attempting to couple the two trains together.

"Our train moved away and came into collision with a stationary train further down the track."

A spokesman for British Transport Police said a full investigation had been launched into the accident.

He said: "It is an operational incident and the Health and Safety Executive will be investigating, together with Railtrack."

The crash comes on the day the not-for-profit company Network Rail takes over the running of tracks, signals and stations from Railtrack.

Adrian Montague, deputy chairman of the new organisation, warned passengers earlier today it would be a "huge job" to transform the railways.