When he died on August 14, 1988, Italy wept. Enzo Ferrari had come to embody all that was loved about motor racing. The poor boy from Modena had risen to the top of Italian society, owned the most glamorous and successful grand prix racing team the world had ever known and cast his shadow across a sport in a way that no one had done before or since.

But a controversial new documentary, to be broadcast this Friday, paints an altogether less flattering picture of the figure who liked to be called “the old man”. Nobody has ever pretended that Ferrari was a saint, and stories of his temper and dictatorial nature abound. But such criticism has generally been couched in hushed tones — as if the great man could reach out from beyond the grave to deliver one of his famous rants.

Many of his closest friends co-operated in the making of the BBC documentary, The Secrets of Enzo Ferrari, but such delicacy has been dispensed with and a far darker side of Enzo’s character emerges. For a start, he was a serial womaniser who regarded the rich buyers of his road cars with contempt. But the film also argues that Ferrari drove his race drivers so hard that many of them ended up dead on the racetrack. Worse still, he went on to have a longstanding affair with the girlfriend of one of his dead drivers.

“If he had been in politics,” says Carlo Benzi, his friend and company accountant, “Machiavelli would have been his servant.”

Enzo Ferrari was born the second son of a metal worker who wanted him to become an engineer. But the young Enzo was no academic. His ambition at that time was to be an opera singer, a sports journalist or a racing driver. None of them required formal qualifications.

After discovering that he had a tin ear and was bad at spelling he began racing for Alfa Romeo in the 1920s. Ferrari was a modest driver himself, only once getting the chance to race in Alfa’s best car, the equivalent of a Formula One machine. It was not a successful experience. He arrived at Lyons, practised, and abruptly went home before the race began. In later life he explained this mysterious episode by claiming he had succumbed to an illness. Friends say it was “ psychological meltdown”.

In 1932, after the birth of his son Dino — who would die in his twenties — Ferrari gave up driving and concentrated on producing winning cars. Over the next 50 years until his death, Ferrari’s iconic red racing cars would win 93 grands prix — more than any other team — plus nine drivers’ championships and eight constructors’ world championships. But such success would come at a price, often paid by the men who drove his cars.

“He would expect a driver to go beyond reasonable limits,” says Tony Brooks, who drove for Ferrari during the 1960s. “You can drive to the maximum of your ability, but once you start psyching yourself up to do things that you don’t feel are within your ability it gets stupid. There was enough danger at that time without going over the limit.”

Motor racing was an infinitely more dangerous sport 40 years ago than it is today. Cars capable of 180mph had none of the safety features of today’s vehicles, and driver protection consisted of a converted polo hat made from canvas and held together with glue. The circuits were often public roads, closed for the duration of the race, lined with trees and stone walls. John Surtees, who won the world championship for Ferrari in 1964, has likened the atmosphere among young drivers to that of second world war Spitfire pilots: every day could be your last.

But even by those bloody standards, the carnage at Ferrari was unusual. In 1957 the dashing young driver Alfonso de Portago, an heir to the Italian throne and boyfriend to the Hollywood actress Linda Christian, came off the track while racing for Ferrari. He skidded into a crowd, killing himself, his navigator and nine spectators, including five children. Ferrari himself was charged with manslaughter, although he was cleared.

The next year Luigi Musso, a dashing Italian driver, crashed in Rheims in the opening stages of the French Grand Prix; two races later the English driver Peter Collins died when his Ferrari spun off the Nürburgring in Germany. The reason for the high death toll is much debated: danger was inherent in the sport, the cars were built solely for speed. But as Sir Stirling Moss has commented: “I can’t think of a single occasion where a (Ferrari) driver’s life was taken because of mechanical failure.”

Viewers of the documentary, however, are left in no doubt as to the reason: Ferrari increased the pressure on his drivers, playing one off against the other and fostering an atmosphere of intense competition for the position of number one driver. “He thought that psychological pressure would produce better results for the drivers,” says Brooks.

Not only that, but Ferrari’s behaviour in the aftermath of such tragedies is questioned. Fiamma Breschi was the beautiful 18-year-old girlfriend of Luigi Musso. After his fatal crash Ferrari bombarded her with letters professing his love for her. “I said I couldn’t marry him,” she reveals, “first of all because I was still in love (with Musso), and secondly because of the age difference.” Nonetheless, Enzo set her up with a house and small shop in her home town.

With so many drivers dying in his cars the Vatican newspaper L’Osservatore Romano described Ferrari as being like the god Saturn, who consumed his own sons. On hearing of the death of Eugenio Castellotti, another of his drivers, Ferrari replied: “And the car?”

In public Ferrari was always careful to acknowledge to the drivers who risked their life for his team, insisting that credit should be split 50-50 between car and driver for any race won. But in private, according to friends, it was a very different story. “He would say that the car was the reason for any success,” says Benzi. “The driver was an accessory.”

He adds: “For the 42 years I worked for Ferrari I only saw him cry once, and that was when he was at the tax office.”