A head-on crash between two Eurostar trains was narrowly avoided yesterday thanks to the quick wits of a driver.

A spokesman for Eurostar said today the 2:42pm service was en route from Waterloo to Brussels when it was signalled on to the wrong track.

The train's driver, whose name could not be confirmed by the spokesman, immediately realised something was seriously wrong, and stopped his train.

A second train, heading towards Waterloo, was only a quarter of a mile away.

Though that train was stopped at a red light at the time of the incident, it is believed that, by stopping his train, the driver of the outbound service may have averted a serious disaster on Britain's railways.

Asked how the train could have been signalled on to the wrong track, the spokesman said it was not for Eurostar to speculate.

Network Rail, the company which took over from Railtrack in 2003, said this afternoon a "serious operational error" had been made, and that the situation was under full investigation.

Delays lasted for around an hour. No one was hurt in the incident.