The signalman at Pilmoor noted the waddling in his log, almost casually: another CemFlo cement train passing through, its wagons rocking side to side in the rhythm that engineers had been worried about for months. Six minutes later, just south of Thirsk, the rear wheel-set of one wagon finally jumped the rails and dragged half the freight train into the path of the southbound fast line. The northbound King's Cross to Aberdeen express, hauled by the prototype English Electric locomotive DP2, was approaching at speed under a Yorkshire summer sky.
DP2's driver was uneasy before he understood why. The next signal should have been visible, but it was screened by what looked like smoke or dust hanging across the East Coast Main Line, and instinct made him ease off the throttle. As he passed signal D19 the picture clarified into nightmare: a derailed cement wagon lying square across his path about four hundred yards ahead. He slammed in the vacuum brake and the locomotive air brake together, dropped sand onto the rails, and shut down his engine in case the wagon held flammable liquid. Then, with the express still moving fast and nothing left to do, he saw the freight train's guard sprinting back toward him through the haze, waving a red flag he could not possibly heed.
DP2 struck the fouling wagon at 15:17 on 31 July 1967. The impact tore the buffer beam, draw-gear, and coupling shackle clean off the cement tank and hurled them seventy-one yards into an adjacent field. The locomotive lurched right; the left side of the cab was crushed, and the left flanks of the first three carriages were sheared open. On coaches two and three this was the corridor side, which spared most passengers. On the leading coach it was the compartment side, and that is where seven people died and forty-five were injured, fifteen seriously. Three of the four main lines were blocked. The undamaged Up Slow line carried the dead and wounded north to Newcastle, and for two days breakdown cranes from York, Leeds, and Gateshead worked the wreckage clear. DP2, the only one of its class, was damaged beyond economic repair and broken up in 1970.
The cause was a tic the engineers had a name for: hunting. CemFlo cement wagons rode on four wheels, and cement dust abraded the suspension components until the trucks began to oscillate laterally at speed - a side-to-side lurch that built on itself. Rolling-road tests at Doncaster after the crash showed flange-to-flange hunting starting somewhere between 24 and 30 mph in wagons judged identical to the one that derailed. The 45 mph limit imposed for these wagons had been a half-measure; the train was below the limit when it came off. British Rail dropped the loaded limit to 35 mph after Thirsk. Two men watching trains at Pilmoor that day remembered seeing one wheel-set drop into a crossover gap and bounce higher than the rest. They had thought little of it at the time. When they heard about the crash, they came forward.
Located at 54.20 N, 1.34 W on the East Coast Main Line just south of Thirsk in North Yorkshire. The four-track main line runs north-south through flat farmland between the Yorkshire Dales to the west and the North York Moors to the east. RAF Topcliffe (EGXZ) lies 3 km to the west; nearest major civil airport is Teesside International (EGNV), 30 km north. Recommended viewing altitude 1,500 to 3,000 feet AGL for tracing the line from York toward Northallerton.