A distracted signalman forgot about a stationary local train that he had shunted on to the opposite running line (the up line) to let an express train, following on the down line, through, as both of the passing loops were already occupied. This led to a collision between a special troop train on the up line and the local train. Immediately afterwards, the express train ploughed into the wreckage. A goods train in the down loop and a train of coal empties in the up loop also became embroiled in the wreckage. In total, 227 people died and 246 were injured — of the 500 soldiers of the 7th Battalion of the Royal Scots on the troop train, only 60 made it to roll call the next morning. The precise number of fatalities is not known because the roll of the regiment was destroyed in the fire. The disaster was made much worse by fire caused by obsolete wooden framed and panelled carriages with gas lighting and the coal from the bunkers of the steam engines.
The accident took place at a change of shift: George Meakin had worked the night shift and was relieved by James Tinsley. These two men had an informal agreement whereby if the local train were stopping at Quintinshill, Tinsley would travel on it to work and save himself a long walk, but this meant he started work half an hour late. This malpractice would have been revealed in the train register that listed the train movements and had to be completed by the signalman on duty. However Meakin recorded all the details of that half hour on a piece of paper and then Tinsley would copy this into the train register when he arrived, to cover up his late arrival. This arrangement and chatter about war news distracted Tinsley so that he forgot about the local train on which he had himself arrived. Both signalmen had fallen into sloppy practices and neglected several standard safety procedures required by the rules.
The accident was exacerbated because one of the trains involved was a troop train. The heavy wartime traffic and a shortage of carriages meant that the railway company had to press into service obsolete Great Central Railway stock. These carriages had wooden bodies and frames, so had very little crash resistance compared with steel framed stock, and were gas-lit. The gas (oil-gas) was stored in reservoirs slung under the underframe. These reservoirs had just been charged and this, plus the lack of available water, kept the resulting fire burning for two days. It was reported at the time that not one lump of coal from the northbound coal train or the locomotives was found after the fire was extinguished, but this may be more exaggerated reporting than fact. The southbound coal train was returning empty wagons to South Wales: it was a Jellicoe Special serving the Royal Navy. The fire probably killed more people than the crash did.
The dead are buried in Edinburgh's Rosebank Cemetery on Pilrig Street. The troop survivors, obviously dishevelled and demoralised, were transported south to army barracks. On their march from the railway to the barracks they were mistaken for prisoners of war and stoned.
The two signalmen, James Tinsley and George Meakin, were sentenced to three years and eighteen months in prison respectively for culpable homicide due to gross neglect of duties.
Quintinshill signal box was also supplied with "lever collars" – devices that should have been slipped over the signal levers to remind the signalmen not to move them until the obstruction had been cleared – but, despite written instructions, the signalmen had got out of the habit of using them. These lever collars are not automatic like track circuits, and hence are not foolproof, but remain in common use to this day.
The fireman of the waiting train had reported to the signal box to remind the signalman that they were at a stand but he failed to ensure that the reminder collars were placed over the signal levers (in accordance with rule 55(g) when there are no track circuits), an omission which landed him in the dock on trial with the two signalmen but he was later acquitted as the prosecution offered no evidence.
The Board of Trade accident report concluded that if the signalmen had followed basic operating rules and used the safety devices provided, the accident would not have happened, and no recommendations for additional equipment or rule changes were necessary.
Meakin and Tinsley were the only signalmen in the UK to be actually given prison sentences for causing a crash. Others have been convicted of manslaughter but were discharged (e.g. Thirsk). However the level of culpability at Quintinshill was much higher, as the Lord Justice General's lucid summing up showed:
The jury returned a unanimous guilty verdict in just eight minutes. Thomas (1969) lists eight separate ways in which the signalmen broke operating rules, mostly regularly, not just that morning.
It is interesting to note that as the incident occurred in Scotland and many of the fatalities occurred at the Carlisle main hospital just over the border in England, differences in Scottish and English law rendered the guilty pair indictable in England for manslaughter, as well as in Scotland for culpable homicide. Under Scottish law, it is the act that results in loss of life (regardless of where the actual death occurs) that has to occur on Scottish soil. However, under English law, it is the loss of life (regardless of where the fatal act occurs) that has to occur on English soil.