The ruthless, disciplined and ambitious Lauda, on the other hand, was "not a party guy", as Brühl puts it mildly. "Niki's was an intellectual approach to life and James' was much more intuitive, visceral and animalistic," Hemsworth says. "On and off the track, they're polar opposites. But they had a mutual respect for each other - it's the yin and yang, and they brought out something in each other."

While this provides the fuel for the film's dramatic engine, is more than just about a clash of personalities. The 10th race of the season was the West German Grand Prix, at Nürburgring. Knowing it to be a treacherous circuit, a week before the race Lauda tried to get the other drivers to boycott it, but failed. His instinct proved tragically correct; on the second lap he lost control of his car, crashing into the barriers. The vehicle caught fire and Lauda was taken to hospital with severe facial burns.

While many expected him to die, Lauda survived - and, after miraculously recovering, returned to compete for the final four races of the season just six weeks after his accident and still in intense pain. The Austrian driver's sheer determination to retain his crown allows for a moment of genius in Morgan's script. Just like Hunt, who gains a new-found respect for his opponent, so audiences are finally able to warm to Lauda.

Yet Howard says some viewers in the US were still confused. "There were a few people in Los Angeles saying, 'Ron, who are we supposed to root for? Who is the good guy and who is the bad guy?' I said, 'That's not this story. This really is a character study. It's a survival story.' The question is, what damage are they really going to do physically and emotionally to themselves as they climb the ladder and reach for this goal, this dream? What price are they going to pay?"

While Lauda almost paid with his life, Hunt's damage was more psychological - an addiction to that need for speed. "His lifestyle off the track, the parties, was another attempt to reach the place [he got to] on the track," says Hemsworth. "But I just loved his attitude - that he was just going to do what he wanted to do, right or wrong." Eventually, it took its toll: Hunt died in 1993, aged just 45, after a heart attack.

Unlike Hemsworth, Brühl was able to spend time with the character he portrays. Lauda is now 64, and "not very diplomatic", the actor says. "In fact, he's very straightforward," says Brühl. "I remember our first conversation on the phone. It was eight o'clock in the morning, and I saw an Austrian number flash up. I picked it up and he said, 'We have to meet, I guess.' And I said, 'It would be good.' Then he said, 'Well, just bring hand luggage to Vienna - in case we don't like each other.' And I just thought: 'Wow, that's how he is.'"

Fortunately, Lauda and Brühl did get on - to the point where the F1 star invited the actor to the Brazilian Grand Prix, flying him there in his private jet. "All the doors were open," says Brühl. "I could talk to [current world champion Sebastian] Vettel before the race, and to Nico Rosberg. I was allowed by the boss of Mercedes to watch the race in the pits, and get the headphones to listen to the team communicating. I met former drivers Jackie Stewart and Nelson Piquet, too, so I got the inside experience of that Formula One circus."

Brühl and Lauda also spent a lot of time talking about fear, which is a crucial theme of the film. "He was talking a lot about analysing fear," says Brühl. "It sounded logical, but it wouldn't work for me. He's a fearless man. That helped me as an actor; I thought, 'I can only be good if I'm fearless myself.'"

Brühl also spoke to Lauda about the accident, although the driver's memory of the incident is cloudy. "I really believe there is a black hole there," says Brühl. "Once, a couple of years after the accident, he smoked a joint and had a flashback. But he got very emotional when he saw those scenes. He said it was incredible for him to relive that - and he's not a man who easily gets emotional."

Howard remains impressed by the rock'n'roll spirit that ran through F1 then. "These guys really did it their way. They really didn't bend to any system. They own their successes and they bear the scars of their journey all on their own."

Now it's all changed - and not just because safety measures have been implemented to protect drivers. Hemsworth notes that there is too much money at stake now to allow rebels like Hunt to have their say.

But back then, out on the track in 1976, it really was anything goes.

opens on October 10