An urgent investigation has been launched after two commuter trains came within seconds of colliding outside Victoria Station.

The incident happened at around 11.30 last night when a Connex South Central train travelling from Victoria to Horsham in West Sussex was allowed to pass through a red light.

All signals at the time were at red because of a signal failure. But at the same time, another Connex train going from Victoria to East Grinstead is thought to have gone through a red signal without permission.

An alert signalman operating from a signal box just outside the station saw that the two trains were converging on each other and cut the power to both trains.

The Horsham train driver reacted promptly by applying his brakes and the two trains halted "within feet" of each other.

Connex said today that the signal failure - at 9.45pm - had affected platforms 12-19 at Victoria.

In such circumstances it is normal for signallers to "talk through" trains which are given permission to pass red signals one at a time.

Both Railtrack and Connex have launched inquiries into the incident.