Most of the dead were soldiers of Royal Scots en route to Liverpool bound for Gallipoli. Their troop train, composed of elderly wooden-framed coaches, collided head-on with an early morning local train. Moments later a northbound sleeping-car express ran into the wreckage. Fueled by escaping gas from the gas-lit coaches, the whole wreck caught fire.

The National Railway Museum blog has a piece about the disaster.

While the disaster is well-known in railway circles, it’s rather disappeared down the memory hole with the general public. It doesn’t loom nearly as large as the second-worst disaster at Harrow & Wealdstone in 1952, or even the Tay Bridge disaster of 1879. Probably the fact that it happened during wartime and the vast majority of dead were soldiers is a major factor.