Lichfield Trent Valley sat on the West Coast Main Line between Birmingham and Crewe, four tracks wide at the station - two fast through-lines for expresses, two platform loops for trains that actually stopped. A local passenger service to Wichnor Junction had come up the slow line, swung across through the facing points at the north end of the station, and pulled into the up platform loop. The driver of the goods train coming behind them - the 14:50 fish from Fleetwood docks to London Broad Street, hauled by Stanier Class 5 number 5495 with seven four-wheel fish vans and a brake van - was expecting to run straight through on the fast line. The signalman in the box at the north end of the station had cleared his signal. From the cab, everything looked correct. The points should have been in the normal position, sending the fish train onto the through line. They were not.

It had been bitterly cold all day. The mechanism of the facing points - the moveable rails that decide whether a train continues straight or branches off - had frozen solid in the position used by the previous local train, the one now standing in the platform loop. When the signalman pulled his lever to reset the points to normal, the rails refused to move. But here is where it became deadly: the rods that connected the signal box lever to the points had been bent by the strain. There was enough flex in the system for the lever to slide all the way home, engage its locking position, and release the protecting signal. The interlocking system, designed precisely to prevent this kind of mistake, was defeated by physical deformation. The signalman thought he had set the route. He had not.

At 18:58 the fish train passed into the station at about thirty-five miles per hour. The driver saw the green signal ahead and would have had no reason to slow down. At the north end of the platform the still-frozen points routed him onto the loop instead of the fast line. There was no time. The Class 5 ploughed straight into the back of the local train. The leading fish van rode up over the brake van of the passenger formation. The rear three coaches of the local - elderly six-wheelers with wooden bodies - disintegrated. The locomotive of the passenger train, LNWR Prince of Wales Class number 25802, was sitting at the front, with its driver and fireman on the footplate; the force of the impact at the rear shoved the entire formation forward and threw the engine itself a hundred yards along the track. The crew survived. Most of the passengers in the rear coaches did not.

Thirteen people died in the immediate impact. Seven more died later in hospital or on their way. The names were ordinary names - returning soldiers, families heading home from New Year's visits, people who had simply chosen the wrong evening to travel. The fish train crew suffered bruising and minor injuries; their driver had to be treated for severe shock, the kind of acute stress reaction that comes from running an express train into a crowded passenger train and walking away from the cab. A porter on the platform was injured by flying debris. The 21 other injured passengers included some whose recovery would take months. The Ministry of Transport opened a formal inquiry. Its report identified the failure clearly: the freezing of the points, the bending of the rods, and the resulting defeat of mechanical interlocking - one of the rarest and most chilling failures in railway safety engineering, because the whole purpose of interlocking is to make exactly this accident impossible.

The Reverend Wilbert Awdry, the country vicar who created the Railway Series of children's books that became Thomas the Tank Engine, took the Lichfield crash and combined it with the Abbots Ripton accident of 1876 to write a story called The Flying Kipper. In Awdry's version, Henry the Green Engine pulls the fish train and crashes into a goods train at a frozen junction, with no fatalities and no terrified passengers - just a young engine learning a hard lesson and a sympathetic Fat Controller. Generations of children have read it without knowing the source. The real Lichfield Trent Valley station is still there, still on the West Coast Main Line. The platforms have been rebuilt; the wooden coaches that splintered that night belong to a different era of railway engineering. But on New Year's Day every year, somewhere in the records of British rail safety, twenty people are remembered for the way frozen weather and bent metal taught the industry to take winter seriously.