Within the walls of a studio somewhere off the M40, Jaguar design director Ian Callum is pacing up and down. There is a sense of anticipation in the room. He is about to give a walkaround talk about a Jaguar sports car, something you might expect him to be able to do in his sleep by now. But there is a difference: it’s 23 years since he last saw this car, and its design had nothing to do with him. Instead, he was tasked with taking its concept and turning it into something else entirely.

I ask him what he’s thinking. “I’m thinking that so much rubbish has been spoken for so long about XJ41, and what it was or was not turned into, that it’s going to be a relief to set the record straight,” he replies.

And so, shortly, he will. For now, however, spool back to the first time that the media was full to bursting with stories of a car called F-type.

The tale of XJ41 and its XJ42 coupé sister (contrary to popular belief, XJ41 was the open car) rattled on through most of the 1980s. It was conceived at a time when the XJS was considered a failure relative to the E-type; Jaguar was determined to make a sports car more faithful to the memory of its greatest roadgoing creation. The project was first mooted in 1980 and was to be spun off the all-new XJ40 platform.

Originally, it was going to be a simple, relatively light car, and had it stayed that way, the course of Jaguar and at least one other car company could have been very different. But as was so often the case in the bad old days of the British motor industry, things started to slip. “For a start,” says Callum, “the car was propelled by a wave of enthusiasm rather than a hard-nosed business case. And then it got delayed.”

Its original launch date of 1986 was pushed back and back, time in which competitors grew stronger, forcing Jaguar to upgrade the mechanical specification, adding weight all the while. What had been intended to be a simple rear-drive sports car powered by a normally aspirated straight six, just like the original E-type, was suddenly perceived to need at least the option of four-wheel drive and twin turbocharging. Development costs spiralled northwards, but still the project continued, despite its weight nearing 1900kg, an appalling mass for a car of the era. It reached the point of being ready for production and would have gone on sale but for one game-changing event: in 1989, Ford bought Jaguar for £1.6 billion.

New boss Bill Hayden undertook a forensic analysis of the business and job one was the kill the F-type. As Callum puts it: “He came in and said, ‘It’s too big and it’s too heavy. This car is a luxury Jaguar cannot afford’.”

That must have hurt those responsible for it, not least Keith Helfet, who’d been responsible for its styling, and his boss, Geoff Lawson, whose post Callum would eventually fill after Lawson’s untimely death in 1999 at the age of just 54.

Between them, they’d come up with a shape that has stood the test of time – a far more attractive car than the ugly XJS and one dramatically more in keeping with the style, if not the execution, of the E-type. Designers are notoriously bad at giving the thumbs up to the work of rival stylists, but Callum is clearly a fan, albeit not without reservation.

“I like it and, at least in design terms, there’s no doubt that it would have worked,” he says. “It’s a very ‘Geoff’ car, a man whose ethos was pure simplicity. If I had to criticise it, I’d say perhaps it’s a little safe and could have done with being a bit more voluptuous. In engineering terms, however, its size and weight meant that Ford made absolutely the right decision to can it.”

And that would have been that, were it not for a maverick Scot called Tom Walkinshaw, who had been commissioned to develop and build the XJ220 (also styled by Helfet) and was looking for the next big thing. It had been his success in racing the XJS that had turned sales of the big coupé around, and it was he who wondered what the XJ41 might be like sitting on an XJS platform.

“The view at Jaguar was that the XJS platform was old, out of date and no longer part of the plan,” says Callum. “But Tom knew it inside out and was convinced he could build an F-type for a fraction of the cost of the one done in house by Jaguar that had just been given the bullet.”

It was a speculative punt – Jaguar never commissioned Walkinshaw to reinvent the XJ41 – but with a majority interest in JaguarSport, he certainly had the ability to get Jaguar’s attention. So he sent over a young designer called Ian Callum – whose most significant work to date had been to style the Ford Escort Cosworth – to see what could be done. And Project XX was born.

“That was the last time I saw this car,” he murmurs today. “This exact vehicle. It was 23 years ago and it seems like yesterday. Weird, really.”

Turning the XJ41 into something that could be built on an XJS platform was anything other than a cut ’n’ paste job. There was no commonality at all between the XJS and XJ41 platforms, the latter being a much larger car with a different wheelbase, tracks and overhangs. But the car started to come together and a clay model was made of an effective downscaled XJ41. “There were little things I didn’t like, such as the grille, so I changed it, which both Geoff and Keith took umbrage at. There were some uncomfortable moments, because effectively I was working on someone else’s baby.

“Then Jaguar said they didn’t want it, which they were entitled to do because they hadn’t asked for it in the first place. All the same, Tom had invested a lot in the car and was not about to let it drop. So one day he came in and said: ‘That Jag. D’you think you could turn it into an Aston?’ Which is exactly what I did. The reason that the clay model of Project XX didn’t survive is because I turned it into the DB7.”

As for the importance of the DB7, I refer to the rather pompous introduction to its road test written by, er, me in this magazine, issue dated 19 October 1994: “The fragile future of Britain’s most distinguished marque is in the hands of this car. Should it fail… the gates at Newport Pagnell could just shut for good.”

How XX turned into the DB7 is another story, because the XJ41 saga still had one more twist to turn. Callum: “Ford turned to Jaguar and said: ‘If Walkinshaw can put a car on that platform, why can’t you?’” Jaguar called the result the XK8 and cashed in big time on a car that was immensely popular and came with a fraction of the development costs of XJ41. That car’s success begat the 2005 XK that remains with us today and upon whose back the company’s current credibility was built.

As we leave, Callum turns and says: “You know, it’s always been an irritation that people think the DB7 is just a rebodied XJ41. I’m glad to have been able to tell it as it is.” But even if the DB7 is related only in concept to the XJ41, that is enough to give it an importance never normally accorded to cars that fail to get into production. As Callum himself says: “Without XJ41, there’d have been no DB7 and no XK8.” There would also, therefore, possibly be no Aston Martin and a very different Jaguar from the company that exists today.

So take a last look at this old soldier, because it might be a while before Jaguar feels inclined to wheel it out again. Jaguar was undoubtedly correct to kill it and wait until the time and its resources were right to do the F-type properly. Even so, I find myself unable to leave without turning and taking one last look. Without XJ41, so much of what we take for granted in two of our greatest marques would simply not exist.