 The first train reached Round Oak at about 8.10 pm; as it drew to a halt a foreman-platelayer heard a loud 'snap' as the coupling behind the eleventh coach broke and 17 coaches and the rear brake van began to roll back down the incline towards Brettell Lane.The booking clerk at Round Oak, seeing the runaway, attempted to telegraph Brettell Lane to give warning, but he was unable to attract the attention of the clerk there.The second train had reached Brettell Lane about eleven or twelve minutes behind the first, and therefore was clear to proceed to Round Oak.