On a number of counts, this is what might be termed 'a bit of a bugger'. Firstly because we had just fitted out test gear and were lined up for the very first acceleration run and thus have no performance figures whatsoever, and secondly because the chaps currently clambering from the Audi were expecting to drive their car back to Italy this afternoon. Oh, and indeed, dear.

It was supposed to be such a simple, straight-forward and thrilling story. July's Goodwood Festival of Speed had attracted many of the post-McLaren contenders for the title of the world's fastest car, so we'd invited them to stay on and join us at a suitably smooth, long runway for a no-nonsense, good old-fashioned performance shoot-out. Initially we got encouraging noises from Pagani, Koenigsegg and Edonis, but come Monday morning only one of them was on its way to the former RAF Bentwaters airstrip, Suffolk, to meet us, our test gear... and a McLaren F1.

Happily, if we had to pick just one of the three, the Edonis would be it. A few weeks earlier, this very car attended a speed test organised by French magazine Sport Auto at the massive Nardo test track in southern Italy where it lapped the eight-mile bowl at a spectacular 359.6km/h - that's 223.5mph. Of the other cars competing, the Ruf R Turbo came closest at 213mph, while the Lamborghini Murci΃©lago clocked 207.7mph, the Ferrari 575M 202.4mph and the 911 GT2 199.1mph. So we have the car of the moment.

Staff writer Jethro Bovingdon and I had secretly hoped to see the Edonis make 200mph on the runway, Jethro because he's young and keen; me because the fastest I've been was a tantalising 199mph (Ruf CTR 'Yellowbird', old N΃¼rburgring straight). It seems our hopes have been dashed, along with something significant in the Edonis's transmission, and I have a good idea what it is.

The concerned-looking trio advancing towards us is Jean-Marc Borel, Federico Trombi and Gianni Sighinolfi, respectively president, general manager and production manager of Modena-based B Engineering, constructors of the Edonis. I'm relieved to note that none of them is carrying anything heavy, though they have good cause for concern. At the close of the Festival, a Scandinavian journalist had performed a dozen tyre-smoking standing starts before hopping out, leaving the Edonis's hot clutch-plate clamped to its flywheel. The two had become fused and only the judicious use of a large screwdriver had prised them apart, small chunks of friction plate breaking away in the process. Thus I had been requested not to work the clutch too hard.

I didn't think I had. With not a little excitement and trepidation, I'd engaged first, dialled in a couple of thousand rpm and let the clutch out. I wasn't going for a full-on standing start but nonetheless there was a gentle, silent letting-go somewhere in the Edonis's drivetrain. The potentially ferocious twin-turbo V12 freewheeled, all drive gone.

It was already baking hot inside the cockpit but you can always rely on a slug of embarrassment to crank up the temperature a notch. I imagined the bellhousing full of friction plate reduced to its original fibres, like the clippings from a barber shop floor, and shuddered at the prospect of the men from B Engineering having to split the engine and six-speed transaxle to fit a replacement.

I'd only seen the Edonis in photographs before it growled into the car park that Monday afternoon. I have to confess I hadn't been overawed. To me it looked like a supercar viewed in a broken mirror, all curious, fractured lines. However, in the metal it was quite stunning - so much more compact than I'd anticipated, so low and purposeful, and the way the cockpit hunkered back into the body's hips, like a fold in rock strata, evoked a sense of speed even when it was parked.

Aesthetically, its bent headlamps still don't work for me but Borel says that, aerodynamically, it's a great shape. It has a low Cd of 0.32 and downforce is positive but modest, so it's stable at speed while squandering little of the 3.8-litre twin-turbo V12's huge power driving through the air. It could have done better than 223mph at Nardo, too, he adds. Apparently, when it was unloaded from the truck, the underside of the front spoiler was disturbed and there was no time to fix it. In perfect trim and with an even longer sixth gear ratio it could crack 400km/h, says Borel, matter-of-factly. That's 249mph, or 8mph faster than the McLaren F1.

Gordon Murray, architect of the F1, has always said that one day there might be a more powerful car that was faster than the F1, but not a more complete supercar. It's a testimony to the design and engineering skills of Murray and his team that only now, a decade after the F1 appeared, is it under threat. The beautifully made Pagani Zonda is more wieldy and exploitable and thus more enjoyable to drive, but at a claimed 205mph, falls well short of the F1's top speed. The Koenigsegg CC is aiming for 250mph but hasn't yet passed full European Type Approval for noise, emissions and crash testing as the Zonda and F1 have. And the Edonis? It is B Engineering's intention to make only 21 cars, using up spare carbonfibre tubs from the Bugatti EB110 project, so full ETA is not being pursued, only drivability and performance, including that extraordinary maximum speed.

B Engineering makes virtually every part of the Edonis, yet even accepting that this is one of two engineering cars sharing development of major systems and is thus far from finished internally, it's hard to imagine the production-approved car matching the exceptional finish and attention to detail of the McLaren. The F1 was a virtually no-expense-spared effort to produce the finest supercar, as reflected in a price tag that is still immense today.

This much is clear when a transporter pulls up and disgorges the only McLaren we could lay our hands on. It's not a regular model but even more special - Nick Mason's GTR, the one and only road-registered example of the F1 that McLaren successfully developed for Le Mans. Much of its carbonfibre is laid bare in the cabin, there's an FIA-approved roll cage and only two seats, the right-hand passenger area being full of electronics and switchgear, but just as on the road car, the finish is exquisite everywhere you look. And when it fires up, well, the sound is simply glorious; even at its fast warm-up idle, the 6.1-litre, normally aspirated V12's note is fantastically complex yet tight, confident and cultured. You know you're in the presence of huge power.

I'll leave it to evo contributor Mark Hales, who's pushed this racer-cum-road car to the limit, to describe the driving experience in detail. A ride in the GTR rekindles memories of the three days I spent driving the F1 when I worked for Performance Car magazine. The central driving position, initially strange, quickly became natural but what I never got used to was the utterly devastating performance. The full-on surge in first and second gear was dizzying in its intensity, literally - a passenger looking the wrong way at the right time could feel suddenly unwell. Just as impressive as that incredible full-throttle punch, which slammed in from little more than tickover and was sustained all the way to the 7500rpm redline (with an extra kick at 5500rpm), was the F1's ability to take off with serious intent, whatever the gear, whatever the revs. Whenever you even tickled the right pedal, the bespoke, naturally aspirated BMW-built V12 delivered instant steam-hammer response, enhanced by a kerb weight of less than 1150kg.

Boy, was it quick. We have the kind permission of Autocar magazine to reproduce the figures from the only independent UK performance test of the F1, conducted back in 1994, with Jonathan Palmer at the wheel. Like any enthusiast, I have certain figures etched in my memory, specifically 0-60mph in 3.2sec and 100 in 6.3.

So we have the benchmark. All we need now is a fixed Edonis. Thankfully, it wasn't the clutch but a driveshaft, which is much easier to replace, and a new one is flown in overnight from Italy.

Twenty-four hours after lining up at the end of the runway for our first run, Bovingdon and I are ready to go for 200mph again. Sensibly we've logged the Edonis's in-gear acceleration before going for the big one, which has given us a taste of its potential. At peak boost (2.5bar, about 35psi) it feels stomach-wrenchingly familiar to me and causes Bovingdon to giggle nervously and ask if I'll be able to spot the braking cone we've placed at the side of the runway. Good signs.

Again I've agreed not to give it a full-on start, but Borel says it's OK to make full-blooded shifts once it's rolling, so above 30mph we should be able to compare its acceleration with the McLaren's. I won't be relying on the rev counter, redlined at 8500rpm, to judge change-ups but a series of shift lights on a panel on the centre console.

It's always more comfortable to be the driver rather than the sack of spuds clutching the laptop, but even I'm stunned by the ferocity of the V12's thrust when full boost arrives. We amble away from the line, the engine growling menacingly at our backs and hit about 25mph before the noise of the turbos spooling up starts to assert itself. There's little sound-deadening on this development car, the sucking and hissing suddenly rises to hurricane force and we're blasted into another dimension, like we're attached to a rocket sled somewhere down the runway and the slack has just whipped taut.

There's no wheelspin; the Edonis simply lifts its nose a fraction and slams forward. I wrench the gearlever back as the first red blinks, there's a momentary lull, the Edonis lunges forward again with similar intensity and in what feels like an instant three greens are glowing again. Cross-gate shifts are always tricky but the lever finds the slot and the rocket sled picks up the slack again.

It's only about two tenths of a mile from our start point to where the concrete changes to asphalt, yet at that point the Edonis is already into third and doing over 100mph! Fourth is grabbed soon after, at about 105mph, fifth at 137mph, and about half-way down the strip I slot top at 170mph. We need to gain 30mph in half a mile to make the magic 200.

Easy? Don't bet on it. Sixth gear is very long and suddenly our runway doesn't feel long enough. Boost is building, but slowly. The braking point cone is rapidly approaching, and just before I switch from the throttle to the brake, the Edonis seems to get on top of the gear and surge forward a little harder. Too late. I hit the brake hard and we're down to 40mph well before the end of the strip. Peak speed? 183mph. Hmm.

After consultation with Bovingdon, we agree to push on a little further past the cone on each run to find the latest possible braking point. Chicken, with high stakes on the side. However, with a best of 188mph, we concede that we don't need an extra few hundred yards to hit 200mph, more like another half mile.

Analysing the data, it's clear that even with a no-holds-barred start, this Edonis, with this development of the ECU, which is still a little way off being finalised, is still some way off the pace of the McLaren. It's an incredibly quick car, hitting 100mph in just 8sec, with a rolling start, remember, but the F1 is still out of reach thanks to its lower mass and instant, massive delivery. Respect is due.

That's not to say the F1's top speed record is safe, though. B Engineering is confident the Edonis can crack 400km/h (249mph) at Nardo. Technical partner Michelin is developing a run-flat PAX tyre that will be tested to 500km/h, and we're invited to be there when the attempt is made. How could we refuse?