Standing in the loop, beside a grain silo, was a goods train, hauled by a 265-tonne (292-short-ton) Beyer-Garratt AD60 class locomotive 6003.

[1][2] The length from the front of the Garratt locomotive to the driver's position contributed to a misjudgment of standing clear of the mainline.

The points at the entrance to the loop were operated by a ground frame and interlocked with signals using annett keys.

There were no track circuits over the points which might have detected the foul locomotive and thus held the home signal at "red" and thus stopped the mail train short of the obstruction.

The impact of the two locomotives colliding forced the Garratt into the side of the silo and reared up its boiler section on to its leading water unit.