Imagine being offered the chance to take part in Britain’s answer to the Le Mans 24-hour race combined with the opportunity to take on the Stig on a proper grand prix circuit, then throw in Richard Hammond’s first high-speed crash since the jet car accident that nearly killed him and you’ll have some idea of the sort of weekend I’ve just experienced.

I’d been asked to drive a Jaguar XKR GT3 in its worldwide race debut. This is a 500bhp car that accelerates, brakes and corners with such force I still ache from the experience. With vast slick tyres and a rear fin for aerodynamic downforce, it looked as though it had just driven out of a Gran Turismo racing game.

As I stood at the side of the Silverstone track and watched the final preparations being made I seriously began to worry that I was out of my league. And then I saw Jeremy Clarkson.

Dressed in his regulation Levi’s jeans and T-shirt with full hangdog expression, he was flanked by his Top Gear buddies James May, Hammond (aka the Hamster) and the Stig. Behind the apprehensive foursome was a more than slightly battered diesel-powered BMW 330d bought, according to Clarkson, “for 10 grand from the back of Auto Trader”.

May and Clarkson had never raced anything much while Hammond’s 24-hour credentials extended to one race – in a 29bhp Citroën 2CV. I noted with amusement the names of “sponsors” painted along the car’s flanks. On one side was Peniston Oils, and with the door opened the last three letters of Peniston were chopped off. On the other side the “L” and “N’s” in Larsen’s biscuits disappeared when the door opened.

We sat through a one-hour drivers’ briefing together and I nervously eyed the mysterious Stig, the man who “forages for wolves at night”, and mouthed across the room: “May the best man win.” He didn’t respond to my attempt at comradeship, but then again his visor was so dark he probably didn’t see it.

Behind my bravado I wasn’t feeling quite so cocky either. Emphatically this was not just another race, but a slice of Jaguar racing history. Back in the mid1970s a private team started racing an E-type – the grandfather of this XKR – and it led, years later, to Jaguar’s famous victories at Le Mans in 1988 and 1990.

Three years later it withdrew altogether from sports car racing. The XKR GT3 I was about to drive marked the return of a Jaguar-backed team after a 14-year hiatus. And I could be the one to stuff it up completely. My co-drivers were Stuart Scott, the car’s owner, plus Chris Ryan and Michael Neuhoff, both proven multiple race winners. It didn’t take a genius to spot the weak link in the chain. Me.

The Top Gear team, filming the race for a new series that starts on October 7, would be competing in the diesel production-car class, running on biodiesel made using crops it had planted during the last series. “Stick that in your tofu and marinate it, Ken Livingstone,” I’m sure I heard Clarkson say.

Our Jaguar preferred a high-octane petrol brew. My team qualified in the middle order, keen not to push it too hard too soon and break something before the race. I was scheduled to drive fourth, which meant I’d not even sit in the car until the race was nearly four hours old. At 8.15pm the Jaguar growled into the pits and I climbed in behind the wheel. Outside it was pitch black.

Endurance racing is a gruelling test for a car and driver. The struggle to maintain concentration over so many hours is compounded by the fact that the circuit is completely unlit with the exception of the pit lane. At night you drive half blind.

There are at least two corners at Silverstone you have to aim at without being able to see a thing. Turning left while driving at a three-figure speed and simply hoping you’ve judged it right is character-building to say the least.

I consoled myself with the thought that if it was bad for me, what was it like for the Top Gear team, competing for the first time in an unfamiliar car on an unfamiliar track?

The Stig and May took the first turns behind the wheel of the Top Gear car. Everything was going smoothly – it was even near the top of its class.

Then it was Hammond’s stint. The danger of an endurance race is heightened by so many different classes of car competing on the same track. At one end of the field you have professional racing drivers in thoroughbred cars.

At the other there are drivers with little racing experience in lightly modified, and much slower, road cars. The Top Gear BMW probably struggled to do 140mph down the straights; my Jaguar was clocking 170mph with ease: the closing speeds were enormous.

And then came the accident. A big beast called a Mosler – a 200mph supercar cum racer I’d been duelling with – clipped the Top Gear BMW with Hammond behind the wheel and sent both cars off the track. I only saw the aftermath as I hurtled by, too focused on my own race to pay much attention. Hammond looked okay – I hoped I was right.

I allowed myself a slight smile at the thought that I was trouncing the Stig (albeit in a different class of car) then my mind returned to the track, where even a millisecond’s inattention could spell disaster.

People always point the finger at the amateur at times like this, but the Top Gear car did have a big cross on a bright yellow background stuck to the back, an internationally recognised sign that there’s a novice driver on board.

It was an unfortunate racing accident, no more or less, in which no one was hurt and both cars rejoined the race after repairs in the pits. I got hit, too, but mercifully without serious damage to the Jaguar. It’s racing and it happens.

Then I had a more serious setback. They say that pride comes before a fall and I should have banished even that slight feeling of smugness that followed lap after successful lap. It was 4am with nearly half the race gone when fifth gear suddenly got very noisy.

With a sequential gearbox you can’t miss it out, so the choice was to carry on regardless and risk a total race-ending failure of the transmission or, as a precaution, bring the car back to the pits and change the gearbox. By now we were closing in on the 10 race leaders so it was an agonising decision. The gearbox change took three hours.

But finish we did, 34th out of a field of 60. Though I say it myself, for a brand new car in its first ever race of any sort, let alone a 24-hour race, it was an astonishing achievement.

No less amazing was the presence at the end of the race of a small black BMW with an impressive array of war wounds. Team Top Gear had made it to the finish in 39th place despite the age of its car and the inexperience of its drivers. To come to Silverstone in these conditions, to compete against a field much better prepared and more expensively equipped than you and still to finish your first endurance race – well, pain me as it does to say so, I take my hat off to them.

Clarkson admitted it had been a tough assignment, one of his toughest ever on the show. After the Mosler incident he reportedly gave Hammond “a comforting hug” during the tense moments while the BMW was being repaired. Hammond looked appalled at the thought. “I’d rather be hugged by a threshing machine,” he said.

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