“Ronnie signed as number two, and I think in a way it didn’t bother him too much. I guess we were looking for different things from the 1978 season. I’d come close in 77, won more races than anyone else, but Ronnie had just been through two or three bad years, and a lot of people thought he was through as one of the leading lights. He really wanted to prove he still had it. There never was any doubt about that, of course.”

Everyone gasped at the elegant beauty of the Lotus 79 when Andretti began testing it at Paul Ricard late in 1977, but it was not to make its grand prix debut until the sixth round of the ’78 World Championship, at Zolder. “Just build me a 78 that’s quick in a straight line,” was how Mario had put it to Chapman, but initially the 79 was unable even to match its predecessor.

“It wasn’t,” Andretti said, “that it didn’t have any downforce as much as the downforce not being in the right place. The car needed a redesign, and until that happened we had to run too much rear wing hence it was slow in the straightaways.”

There was another problem with the early 79, too. Chapman, ever seeking lightness, was keen to have a new gearbox in the 79. Designed in-house, and built by Getrag in Germany, it was indeed smaller and lighter than the customary Hewland, and also permitted faster changes until it began to stiffen up, which it always did.

“I actually raced the car for the first time in the International Trophy at Silverstone,” Mario recalled. “By now the redesign work had been done, and the grip was unbelievable. That was when I fell in love with the 79. ‘Colin,’ I says, this car is something else again but we can’t compromise it with that gearbox: we have to use a Hewland.’”

Reluctantly Chapman acquiesced, and by the time of the Belgian Grand Prix the car, in more or less definitive form, was ready to race. Andretti put it on pole position, by almost a second, and led all the way, with Peterson following him home in the old 78.

A fortnight later, at Jarama, it was the same story, save that now Ronnie, too, was in a 79. The two black cars made up the front row, and finished 1-2 Andretti ahead by 20 seconds. At Anderstorp Mario retired, but at Paul Ricard normality returned: Andretti first, Peterson second. In their wake the rest looked rather breathless.

The Lotus 79 was one of Cohn Chapman’s quantum leaps; as the 78 had been the first ‘wing’ car, so it was the 79 which introduced ‘ground effect’ to grands prix. “The Cosworth never had the horsepower Ferrari did,” Mario said, “but it didn’t matter. We were pretty good on top speed, and whenever the road turned, Ronnie and I were just off our own…”

Neither 79 finished at Brands Hatch, but Andretti won again at Hockenheim, and Peterson was never better than at the Österreichring, where he triumphed in appalling conditions after his teammate had crashed. At Zandvoort they finished nose to tail, Mario ahead. With three races to go, he led Ronnie in the World Championship by 12 points, 63 to 51.

At Brands Hatch, Peterson had out-qualified Andretti for the first time, and it was here that Mario chose to reveal a clause in Peterson’s contract. “It said that if we were running at the front, with no problems, then I was to win. Like I said, I felt that I’d earned that from the work I’d done in previous seasons, and Ronnie accepted that. More important, he gave his word.

“Colin was furious with me for letting that out, but I did it in fairness to Ronnie: I didn’t want people thinking I was passing him because he couldn’t keep me back. We had made this agreement, and it wasn’t something Ronnie or I felt bad about.”

It truly wasn’t. By now Peterson had achieved his objective, re-established himself and signed to drive for McLaren in 1978. That being so, another driver suggested at Zandvoort, he should forget about the Lotus agreement, and go all out for the championship.

Ronnie was appalled at that. “I gave my word, and I’ll stand by it,” he said “Apart from anything else, Mario deserves the title this year because he was so far ahead of me in the first half of the season.” Peterson also acknowledged that, without Andretti’s skills as a test driver, the 79 would not have been the car it was.

Thus they went to Monza. “I had no worries about Ronnie,” said Mario. “Even when I knew he would be leaving the team, I trusted him absolutely. In spite of what people had forecast, the friendship between us just got stronger and stronger as time went along. The day after Monza, I had no feelings about being world champion; Ronnie’s death just put everything else out of my mind…”

At Goodwood, Andretti was back in his 79 for the first time in 20 years, and hammered up the hill, delighting the crowds. “Lot of memories come back with this car,” he murmured. “Probably more than any other from my career. The most beautiful race car of all time? I think so, don’t you?”