He sprang to prominence with Lord Hesketh's eponymous team in 1973, when he moved over from the March company to engineer Hesketh's privately owned March 731G for a young Englishman called James Hunt.
Few took them seriously; Postlethwaite held a BSc and a PhD in mechanical engineering from Birmingham University, which had taken him to ICI in 1968 as a research specialist in advanced materials, and had three years' experience at March, but was still an unknown. Hesketh was seen as little more than a playboy, and Hunt had been written off by most after a series of shunts had seen him sacked the previous year by March. But they melded together brilliantly, their outward irreverence masking steely determination. Soon Hunt was running in the top six. By the end of the year, as the works March flopped, Hunt was challenging Ronnie Peterson and Lotus for victory in America.
The following year he won the non-championship Daily Express International Trophy race at Silverstone in Postlethwaite's first Hesketh car, and ran strongly in the Grands Prix. A year later still, Hunt scored a brilliant victory in Holland over World Champion-elect Niki Lauda's Ferrari, driving a developed version of Postlethwaite's racer.
Postlethwaite moved on to the Wolf team in 1977, when Jody Scheckter won first time out in Argentina, before adding two more successes. Then followed Postlethwaite's Italian era with Ferrari. Settling fluently into the Italian way of life, he dragged the Scuderia into the modern era as he laid the foundation for today's English influence within Ferrari's technical department.
In 1982 and 1983 the team took the Constructors World Championship with Postlethwaite's designs. Later, he would play a key role in the development of the semi-automatic transmission that is now ubiquitous, and which has removed the missed gearshift from the racing driver's book of excuses. When he moved in 1988 to the first of his two spells with Tyrrell (the second was in 1994), he and the aerodynamicist Jean-Claude Migeot pioneered the raised nose which is also now universal.
Postlethwaite's forte as a designer was down-to-earth pragmatism combined with a probing mind. An unusual shape for the Hesketh March in 1973 was nicknamed "Silly Nose" within the team, but was in fact a clever development of the wide "splitter" style of nose that would also become widespread.
Sometimes one was tempted to believe that there were two Harvey Postlethwaites, Happy Harvey and Horrid Harvey. When the mood took him he could be abrupt. Once, as a tentative sprog reporter in Brazil, I asked him if he had a moment to discuss how the Ferraris had gone in qualifying, as he stood alone, staring at the sky, during what seemed a quiet moment. "No," he retorted trenchantly. When reminded of the incident years later, he was genuinely embarrassed. It wasn't that he was intentionally rude, more that there were times when he was totally preoccupied, wrestling mentally with a technical problem.
Last year we were discussing his vision of F1's future in Japan, when suddenly he said, "Never mind all that crap. How's life since you went freelance? Are you having a good time?" Privately, he clearly thought a lot about the people he shared paddock space with. He had the rare distinction of being one of those characters you wanted to bump into in the F1 paddock. He was amusing, passionate and irreverent, but also clever and willing and able to explain technicalities to the lay mind.
Mike Gascoyne, the technical director at Jordan who was his number two at Tyrrell, said: "Harvey was a defining figure in my career and the careers of many other young engineers. His infectious enthusiasm for both engineering and motorsport was an inspiration to all those who had the benefit of working with him."
Most of the time he exuded thoroughly outgoing bonhomie. He was not dissimilar in either appearance or manner to the land speed record ace Richard Noble. It was something of a joke that, since nobody had ever seen them together, they must therefore be one and the same person, because they shared so many personality traits.
The Tyrrell team regularly hosted a press dinner in the paddock during the French Grand Prix at Magny-Cours. Postlethwaite - also known as "the Doc" - loved the event and the social banter, and was a fund of hilarious anecdotes. He would rub it in good- naturedly if anyone dared to miss the party because of a prior engagement. Last year's dinner was the end of an era, for it marked the last for Tyrrell, which had been sold by its founder Ken Tyrrell and was soon to be branded British American Racing. It fell right in the middle of one of England's televised World Cup matches, which ensured that it was a riotous success.
In his new role co-ordinating Honda's test programme, before the company's planned re-entry into F1 in 2000, Postlethwaite remained outspoken on technical matters. "I would like to see a far greater freedom of electronic control systems," he said. "I think we are being too black and white. It was probably right four or five years ago to put a brake on some of these things because they were getting a little bit out of hand, but I think now that we understand them better and that the governing body is in a position to police them a bit better. We ought to be allowing more. I do really think it's a bit silly when there is more sophisticated control on your road car than there is on an F1 car. F1 should be a product leader really, not a product follower."
But he was not too vain as an engineer to play down the role of the driver. "If I had to go out and spend a budget to go F1 motor racing, I would spend a great big chunk of it on getting the best possible one," he said. "The day we put Jody Scheckter in a Wolf was the day the team went whoosh!"
Harvey Postlethwaite, mechanical engineer: born 4 March 1944; married (one son, one daughter); died Barcelona 13 April 1999.Reuse content