The XJ's engine also benefitted from a timing chain, rather than a belt. So many cars on my list used cambelts, which were all no doubt long past their recommended servicing intervals. I dreaded the thought of hearing a distant 'snap' and the subsequent terminal chatter of valves being introduced to pistons at a vast rate of knots.
A quick bit of bistromathematics suggested that the Jaguar was theoretically geared – on its current wheel and tyre combination – to do over 160mph. I just hoped the XJ wasn’t a tachophobic. It was advertised for £575, but I figured the seller would probably take £500 cash for it and put in a call.
Two days and a holding deposit later, the XJ proved to be much as expected: a well used 18-year-old example with some minor dents, light corrosion, missing bits of trim and a tired driver’s seat. Everything important worked, though, and the car was very solid overall. Four decent matching tyres also made me feel a little more confident. A quick test drive revealed it to be delectably wafty, so, with the negotiations completed, it was mine.
With the Jag safety checked, cleaned and topped up with fluids, we headed up to Bruntingthorpe proving ground in Leicestershire. Its two-mile-long runway would hopefully give me enough room to find the Jaguar’s terminal velocity in complete safety, and there was plenty of space in which to recover if things went awry.
An initial sighting lap, taken at a gentle pace, revealed that the Jaguar was more than happy to tick along at 100mph. It was steady, tracked straight and was only moderately perturbed by the crosswinds that gusted across the track. More impressive was the fact that it stopped in a swift and controlled fashion.
I donned my helmet and, after one last pre-flight check, it was time to open the taps and see what the venerable XJ could really do. I put the transmission in Drive, switched into Sport mode and, with the rear wheels almost hanging off the runway, let fly. At the halfway mark the timing gear indicated 110mph, and as I neared the braking point it had just nudged up to 131mph.
That wasn’t to be sniffed at, but I got the feeling the stately old Jaguar didn’t have much more to give. What did surprise me, however, was how effortlessly it had done it. No vibrations, no issues – no mechanical protestations at all.
I chose to run the Jaguar through the gears manually on our next attempt. It fluttered against the limiter briefly in second, throttle pinned to the floor, and surged onwards with much more conviction when I shifted into third. The improvement was notable, and it clocked an impressive 140mph at the end of the straight, passing a startled and bemused biker who had nailed his Triumph Tiger Sport to its maximum of 135mph.
In an effort to eke more out of the Jag, a colleague and I set about cutting drag by taping it up around the nose, bonnet and door seals. We also ditched the spare wheel, rear seat squab and some interior panelling to cut the weight. It was a quick, rough job but nothing ventured, nothing gained. With my new, aerodynamically revised and lightweight XJ warmed up, I headed out for what I hoped would be the fastest run of the day.
The Jaguar sprang from its trap and barrelled down the runway, tracking arrow-straight and true. One-thirty flashed past on the speedometer and the revs were still rising. The Boeing 747 parked at the far end of the runway was growing disconcertingly large in the windscreen. One-forty. With my left foot hovering over the brake pedal, I pushed on until the ‘point of no return’ cone flashed past. Hard on the brakes, down a gear, off the brakes and into the escape road. I glanced up at the timing gear. We’d managed 141mph.