At 5.30 a.m on 18 February there was a head-on collision on the single track branch line 1 ½ miles from Hallen Marsh Junction going towards Pilning Low Level. The night was very dark, clear and frosty, with 3 inches of snow on the ground. Signalman J. Wheeler was on duty. He was 22, had been a signalman for 3 ½ years, the last six months at Hallen Marsh Jc. At 3.41 a.m that morning he had the 1.45 a.m Cardiff to Avonmouth goods standing at the Home signal on the branch while a banking engine ran across the junction, on the Up Main towards Henbury.
With the engine clear, Wheeler pushed lever 14 into the frame, setting the points for the branch, and reversed 16 which closed the catch point in the branch line and reversed 51 lever so as to turn the crossover from Up to Down Main. He pulled signal lever 40 and the train set off for Avonmouth. When it had gone Wheeler replaced lever 51, setting the crossover points for ordinary – Up and Down – running but did not re-set 14 or 16. The route remained set for ‘Up Main to Up Branch’.
At 4.37 he accepted under the ‘Warning Arrangement’ from Pilning Low Level the 8.45 p.m Cardiff – Avonmouth goods and at 5.10 that train passed Pilning Low Level. The train was 2 ½ miles away. At 5.18 a.m Wheeler accepted at ‘Line Clear’ the 9.20 Avonmouth to Salisbury goods. He got ‘Line Clear’ from Henbury and lowered his Advanced Starting signal, lever 63, which was the Henbury side of the junction but when he tried to pull lever 65, his Up Main to Henbury line starting signal, he was unable to do so because the route was set for the branch. Signal 65 was the directing signal for the junction, to its left was Signal 62 which was cleared when the route was set for the branch. When the 9.20 p.m Avonmouth came to a stand at signals 62/65 Wheeler told the driver that the lock had failed on the operating lever for the main line route but all was in order – he could pass the signal at danger and proceed towards Henbury.
The driver set off, Wheeler sent ‘Train entering Section’, 2 beats on the bell, to Henbury and then went to his Train Register to enter-up times. He had his back to the train. When he looked up he saw that the train was going along the branch line and had passed the branch advanced starting signal – 61 – at Danger and showed no sign of stopping.The driver must have thought there was a reason for him being sent the very long way round to get to Filton Junction and was working his 68xx class 4.6.0 hard to accelerate his 600 ton train. Signalman J. Wheeler was now faced with the terrifying knowledge that a head-on collision was inevitable and when he heard the awuful thumping, crunching, sounds 1 ½ miles away he telephoned Bristol Control with the news.
The 8.45 p.m Cardiff, hauled by a ‘Dukedog’ 90xx class 4-4-0 with 350 tons was travelling slowly because the driver had been ‘Warned’ to be ready to stop at Hallen Marsh Junction. The closing speed was estimated at 37 mph. The view ahead from the Cardiff train was so restricted that the driver had no time to apply his brakes or blow his whistle. Both engines and their tenders were de-railed, all six men of the two trains were injured. Twenty six wagons were derailed some of them were petrol tankers; other wagons were smashed to bits. Clearing the line was delayed by having to clear away so many wagons before they could get a crane to the derailed engines. The collision happened at 5.30 a.m on the Tuesday. The line was clear and fit or normal running at 6 p.m on the Thursday.
The Inspector of Accidents for His Majesty’s Railway Inspectorate was Brigadier Langley. At the end of his report he wrote: I have no recommendations in connection with this accident. There is no justification for the provision of safety equipment. It required successive mistakes by two men to cause the accident. The young signalman jumped to a wrong conclusion and an experienced driver passed a signal at danger without authority and did not notice he was on the wrong route.