Coton Hill sits on the northern edge of Shrewsbury, where the railway from Chester and the Welsh Marches descends to join the main lines through the town. The Hencote incline runs at 1 in 100 - a steep grade for a heavy freight train. The rules of the day required Class 5 freight trains, the heaviest classification then in use, to halt at the top of the gradient before proceeding. The halt let the crew check brakes, set sand if needed, and confirm signal aspects ahead before committing to the descent. It was a familiar piece of railway practice on any line with a steep approach to a junction. On the morning of 11 January 1965, for reasons the inquiry never fully resolved, that halt was not made.

Past the stop sign the train accelerated. The driver appears to have applied the emergency brake at some point - the inquiry found evidence of emergency brake applications - but the train was already running away. It entered the Coton Hill goods loop at speed instead of being routed onto the main line. At the exit of the goods yard, where a set of trap points was designed to derail a runaway rather than let it foul the main running lines, the locomotive jumped the rails. It travelled another seventy yards before crashing into the Coton Hill South signal box, demolishing the structure completely. The signalman on duty inside was killed. The driver of D1734 was seriously injured but survived. He had no memory of the accident afterwards.

The destruction did not stop with the signal box. The first eleven wagons followed the locomotive into the wreckage. When the signal box was destroyed, the points behind it - controlled from inside - opened uncontrolled, and twenty-four further wagons rolled into a siding where they derailed in turn. Some of them collided with a second Class 47 diesel that had been waiting to leave the yard. Hydrochloric acid leaked from one damaged wagon, hampering the clean-up. The line was completely blocked. Normal service did not resume until 14 January, three days later. D1734, the nearly-new locomotive at the centre of the disaster, was beyond repair. Despite being only eight months old, it was scrapped.

The Department of Transport inquiry made its findings methodically. Because of the damage, it was impossible to determine whether a brake failure had impaired the driver's ability to stop the train. But the inquiry concluded that even if there had been a brake failure, the driver would have been able to stop safely had he obeyed the stop sign at the top of the incline as required. The driver was therefore held responsible. The most plausible reconstruction, the inquiry suggested, was that he had assumed the points were set for the main line rather than the goods loop, and had failed to make the mandatory halt. He could not confirm or deny it. He had no memory.

When D1734 was being broken up some months later, the strip-down revealed something that had not been visible at the crash. The locomotive's Automatic Warning System equipment - the cab-signalling device that would have given the driver an audible alert if signals were set adverse - had been isolated, despite appearing to be in working order. The inquiry noted the fact but pointed out that the AWS would not have made any difference. The signals had not been against the driver as such; he had missed a fixed stop sign, not a signal. The AWS would not have warned him about that. Still, the discovery raised uncomfortable questions about how much of the cab equipment on that particular locomotive had been quietly worked around by crews. The signalman who died had no part in any of those decisions. He went to work that morning to operate his signal box on a normal night shift. He was killed by a chain of failures that began somewhere down the line and ended in his workplace before dawn.