With no working brakes, the wagon - laden with 16 tonnes of steel railway track - ran away down a slope and hit a group of maintenance workers, killing four.

The men were killed when the runaway wagon ran into them at about 40mph on a section of the west coast main line near Tebay, Cumbria, almost two years ago.

Mark Connolly and Roy Kennett are accused of four counts of manslaughter.

The four men who died were Colin Buckley, 49, of Carnforth, Lancashire; Darren Burgess, 30, also of Carnforth; Chris Waters, 53, of Morecambe, Lancashire; and Gary Tindall, 46, of Tebay.

The wagon, which weighed 19 tonnes, came out of the morning darkness and hit the gang of railway workers at about 40mph. The men died almost instantly, Newcastle Crown Court was told.

Their families, sitting in the public gallery, broke down in tears as the prosecutor said they suffered massive injuries, including loss of limbs.

Opening the case for the Crown, Robert Smith, QC, told the jury that both defendants were "grossly negligent" in their actions.

He said Connolly had deliberately disconnected the hydraulic brakes on two wagons, while Kennett had operated the wagons knowing they were faulty.

In the case of Connolly, he dismantled the brakes for "financial gain" because it was cheaper than repairing the wagons properly.

Connolly, 44, of Coedana, Llanerchymedd, Anglesey, North Wales, and Kennett, 28, of Hollingbourne, Maidstone, Kent, both deny four counts of manslaughter.

Connolly also denies three counts of breaching health and safety laws, and Kennett denies one.

Mr Justice Holland adjourned the trial until today.