In July 1960, in a siding at Derby scrap men cut up a black locomotive whose number had been 10100. When the torches went out, nothing remained of the most mechanically complex locomotive ever built in Britain but a tabletop model in a museum. The machine had beaten steam over the Pennines, cleaned the tunnels it ran through, and kept its expresses on time for years. It had also been an orphan from the day it was born, an idea the entire industry had decided against before the first drawing was even finished.
The idea belonged to Louis Frederick Rudston Fell, a lieutenant colonel who had spent the First World War rebuilding aero engines in France. He had come home with a deep conviction about the internal combustion engine and an unusual background: a gentleman by birth, a craftsman by choice, a man who had built a motorcar with his own hands alongside his mother. By the late 1940s, after decades at the center of British engine design, he had reached a conclusion that put him against nearly everyone in his profession. The diesel electric locomotive, the industry’s obvious answer to steam, was in his view a power station on wheels: heavy, expensive, and wasteful.
His alternative was radical. Instead of one enormous engine driving a generator, he proposed several small, mass-produced diesel engines whose power would be combined mechanically. His locomotive would be built by railwaymen, using ordinary engines and gearboxes, with no electrical firms involved at all. In 1948, the newly nationalized British Railways agreed to build a single prototype.
Henry Ivatt, chief engineer of the London Midland region, welcomed the scheme because it promised work for the Derby workshops he loved. A consortium was formed, backed by Shell and by Sir Harry Ricardo, whose combustion chamber design would sit inside every cylinder of the new machine. Four 500-horsepower Paxman engines would drive the wheels; two smaller AEC engines existed solely to drive the blowers that forced air into the rest. Sixty combustion chambers firing inside one locomotive, six engines aboard, all of it fed through a single gearbox.
The gearbox was the heart of the design, and it worked on a principle nobody had tried before. Fell had taken the ordinary differential from a motorcar and run it backwards. Instead of one engine splitting power to two wheels, he fed power in from two engines and took the combined output out through a single shaft. Two pairs of engines fed into a final differential, delivering four engines’ worth of power to the driving wheels.
Each engine connected through a fluid coupling that could be filled or emptied with a flick of a lever, allowing the driver to bring engines in one at a time as the train gathered speed. The transmission did not multiply pulling force; it added speed. The full tractive effort of the locomotive was available on a single engine. The others were there to let it go faster.
Built in the paint shop at Derby through 1949 and 1950, the locomotive emerged in plain black, numbered 10100, the only diesel mechanical among the experimental prototypes British Railways was testing. When her builders first tried to move her under her own power, she refused to budge. The cause, found the next morning, was a disconnected pipe that had left the brakes on. With the pipe reconnected, she moved.
In early 1951, she began running trials. Her starts were smooth where steam locomotives lurched and slipped. Her engines ticked over so quietly that one man compared her to a luxury motorcar. When they wired her air horns, someone crossed the connections, and she sounded a soft minor chord, more organ than locomotive.
Nobody troubled to correct it. On the Settle and Carlisle line, climbing the long gradients with a dynamometer car recording her efforts, she proved that four small engines and a mechanical gearbox could haul a real train over real mountains. She entered scheduled passenger service in 1952 on the Midland main line out of St Pancras, over the Pennines to Manchester, hauling twelve-coach expresses. Driving her was unlike anything else on the network.
The driver started on a single engine, which carried the train up to about six miles an hour. Then he brought in the second, good for seventeen. The third took the train to twenty-four. Only with the train rolling did he engage the fourth, which ran her up to her authorized limit of seventy-eight miles an hour.
It was changing gear by summoning whole engines to life, one after another. She found a driver who mastered her completely. Jim Low could read the machine through his boots and palms, and he played the four levers like an instrument. His trains ran to schedule, over the hardest railway in England.
An old steam driver who took her out preferred her to anything else he drove, a remarkable thing among men who felt the coming of oil as a loss. The Fell was reckoned to be about twenty-five percent more powerful than the Jubilee class steam locomotives she ran beside. On difficult starts, Low had found a way to play the oil scoops of the second, third, and fourth engines in a practiced sequence, using the spinning inertia of their fluid couplings to add to the pull of the first engine, giving her a sharper getaway than her design was supposed to allow. She kept time, and she cleaned the tunnels: her side blast scoured decades of steam soot off the walls, until trains behind her arrived at the far portals showered in the loosened grime of a century.
She was, as the Paxman engineer John Cove later put it, extensively tested, and she proved the viability of an entirely mechanical drive for a locomotive of that power. That was the summit of the whole undertaking: one black locomotive, running well, quietly proving that an entire industry had been wrong. But the tide had already turned against her. The electrical firms had built their diesel electrics and had the ear of the men who would decide the future.
And the Fell was built on a principle that made her utterly alone. Everything aboard was driven mechanically, no electrical shortcuts. Long shafts ran the length of the machine, driving fans and pumps through gears and couplings. The cooling system, with radiators at the ends of the locomotive, trapped air and ran hot.
The screaming auxiliary engines blew their head gaskets. And everything she had poured into one gearbox. If the gearbox failed, she did not limp. She stopped completely.
In July 1952, a single bolt failed somewhere in the upper part of that great gearbox. It fell into the gear train and was carried down through the whole of it, smashing between the turning wheels, rendering most of the gears unfit for service. There was no spare gearbox. There was only one locomotive.
She was out of service for over a year. John Cove believed this failure probably influenced British Railways’ decision not to proceed with a planned second, improved version. In his judgment, it was effectively the end of the project, years before the machine was finally scrapped. She was rebuilt and returned to the Manchester expresses.
But she was damaged in a way that was never quite put right. The next blow came from a quarrel between two men. Her axle bearings were American taper roller bearings, a first for British mainline locomotives, and they needed their oil reservoirs kept topped up. The manufacturer had seconded a fitter to look after them.
At some point, the fitter and one of the railway men had a row. After the quarrel, the topping up simply stopped. The fitter would not do it, and the railway would not do it either. Nobody did it.
Near Luton, a bearing starved of oil ran hot. When they investigated, of the seven axle boxes still in service, four were bone dry, and the others held only rainwater. To move the crippled machine, Jim Low used his old virtuoso’s trick, forcing the transmission to drag a seized axle clear. The gearbox, already shattered once and painstakingly rebuilt, was strained past its limits.
After that, she was never the same. As she sat broken down, an English Electric executive passed on another train, leaned out of the window, and shouted at the stricken machine: See what I mean? In January 1955, British Railways announced the Modernisation Plan, a commitment of over a thousand million pounds to drag the railways out of steam within a decade. It committed the network to diesel electric transmission as the standard for mainline power.
There was no line in the plan for the diesel mechanical. The Fell’s whole approach was not defeated in a fair fight; it was simply written out of the future by a committee. For Derby, the plan was a catastrophe. The works the Fell had been meant to save were gutted.
Hundreds of part-built steam locomotives were scrapped unfinished. The skill drained away. In 1955, the consortium that owned 10100 sold her to British Railways, and Fell Developments Limited was quietly wound up. She ran on through the middle of the decade, damaged gearbox and all, an orphan doing her orphan’s work.
On the 16th of October 1958, at Manchester Central, an oil-fired boiler used only to heat the passenger carriages caught fire. The damage was severe. She was towed home to Derby and left in a corner of the yard in sidings the railwaymen called the Klondike. Nobody ever wrote down who decided not to repair her.
She was simply deemed not worth the saving. Through the winter and into 1960, she was slowly stripped of parts. In July of 1960, the remains were cut up for scrap. There was no ceremony, no last run, no preservation.
Louis Fell was sixty-six when his locomotive was scrapped. He gave away all his patents to Rolls-Royce, who gave him a department in return. He gathered his people and built a new locomotive called DHP1, the true heir of 10100, using the same distributed-power principle with modern torque converters. It never hauled a single revenue train.
It was broken up in 1967. Fell died on the 27th of November 1977, aged eighty-five, and was buried in a quiet Lincolnshire churchyard. He lost every battle, and the idea won the war after his death. Every diesel multiple unit, every sprinter, every TransPennine express that runs over the very peak the Fell once climbed carries its power distributed among small standardized engines spread through the train.
The principle Louis Fell drew on a drawing board in a bedroom became so completely the ordinary way of things that nobody any longer sees it. Of the locomotive itself, almost nothing survives. A handful of photographs, a bleak image of her being cut up in the yard. And in the National Railway Museum at York, in the open store, there is a working model of the Fell transmission, built by Rolls-Royce, small enough to sit on a table, its gears still turning, still demonstrating the backwards logic of the power-adding differential.
That is all that remains of the strangest locomotive Britain ever built. It just turns, which is in the end all the colonel ever wanted it to do.
