There’s a very good reason why Top Gear never allows its tame racing driver to speak. It’s because he might express an opinion, and the opinions of all racing drivers are completely worthless.

You could put one in a Bugatti Veyron and while he might have a few kind words to say about the power, he’d dismiss the steering, the brakes and the grip as rubbish.

To a racing driver, a BMW M3 is crap, an Audi RS4 is terrible, a Lamborghini Gallardo is gutless, and as for the Aston Martin Vanquish . . . oh dear. Damon Hill drove one once and wondered every time he put his foot on any of the pedals if perhaps something had broken.

Michael Schumacher is no better. Many years ago he hurled me around some sinewy ribbon of a track in a Ferrari 575, and in every corner the V12 wail was drowned out by a series of guttural Germanic expletives. He moaned about the understeer, the lack of grunt, the gearbox and every other feature of what I thought was a pretty good car. Then when he got out, he declared it to be s***, and went to the bar for an orange juice.

This has always annoyed me . . . until earlier this month when, for the first time, I drove a proper racing car, in a proper race. And now I know exactly what racing drivers mean. All road cars – every single one of them – are useless.

My racing car was a BMW 3-series with a diesel engine. It had covered about a million miles, ferrying PowerPoint equipment, I should imagine, to and from various out-of-town business hotel conference suites. So as a result, I was able to get it for just shy of £11,000.

It was then taken to a workshop where all of the interior was replaced with a roll cage and one seat and a fire extinguisher. Underneath, we simply fitted better brakes, lowered suspension and slick tyres. As racing cars go, then, it was far removed from a McLaren-Mercedes. Think of it as a worn-out fat man in a tracksuit and running shoes.

But oh my God. The tiny changes we made transformed this humdrum little rep-mobile into a car that was more exciting and more fun to drive than any supercar. No really. Give me the choice of driving around Silverstone in this, the world’s worst racer, or a Zonda, one of the world’s best road cars, and I’d take the diesel in a heartbeat.

At the track, I started out braking for the bends where I would brake in a road car. But this caused the BMW to just stop. Immediately. So then I’d have to engage first and accelerate up to the bend I had been trying to slow for. It was not a good look and many spectators laughed.

Quickly, I realised I could brake about 6in before the turning-in point and even then I wound up going too slowly. On slicks, a car will go round any corner at any speed that takes your fancy. No really. Through Stowe corner, a Lexus road car is right on the raggedy edge of controllability at 70mph. In our diesel you could take it at 100mph . . . while doing a crossword.

After a weekend spent revelling in the incredible grip and the braking, I climbed into my Gallardo for the trip home and it was like I’d inadvertently got into a time machine and gone back 200 years. It would go all right but it wouldn’t stop and it wouldn’t grip.

Finally, then, after 20 years in the business, I began to see why racing drivers don’t like road cars. It’s simple. It’s because any car designed to cope with speed humps and potholes, any car fitted with tyres that last more than an hour is bound to be less capable than any car designed purely to go round corners as fast as possible.

I therefore find myself this morning hooting with derision at the current crop of so-called track-focused road cars. The Porsche GT3 RS is a classic case in point. Yes, it has a roll cage and, yes, it’s jolly light. But will it corner as fast as a diesel BMW on slicks? No. Will it brake more abruptly? No.

All Porsche has done by lowering it and firming it up and removing the soundproofing is make it noisy and uncomfortable on the road. Does it work on the track? No. In the big scheme of things, not even slightly.

The only way you could do that is by fitting slicks. But if you do that and try to drive home afterwards, the constabulary will want a word.

Then there’s the bothersome business of cost. A full exhaust system for an M3 costs BMW £76. That is cheap. And cheap doesn’t work on a racetrack. After our 24 hours, for instance, we got a bill for tyres that amounted to £6,000.

I’m sad to announce, then, that road cars and track cars are two separate entities and that neither will work, no matter what you do, in the other’s domain. A racing car on the road will be brutal, unforgiving and noisy. A road car on the track will go into a barrier and kill you.

Imagining, then, that your GT3 RS or your Gallardo Superleggera or your M3 CSL gives you a feel of the racetrack is as mad, I’m afraid, as imagining that if you eat a rasher of bacon, you’ll have an idea what sausages taste like.

It is very difficult to build a car that can do two things, a point demonstrated this morning by the meat of the missive – the Volvo XC70.

What we have here is a normal five-seater Volvo estate car, converted with some stilts so that it can get down your rutted driveway without losing its sump to a stone.

Sure, it can’t climb the north face of the Eiger, and it would come unstuck if it were pressed into service with the Highland mountain rescue service but because of the extra ground clearance and four-wheel drive it’ll be fine when you go to those parties where you’re made to park in a muddy field.

In theory this is excellent. Because it isn’t a proper off-roader, environmentalists won’t throw eggs at it and leave insulting messages under the windscreen wipers whenever you leave it alone for a moment. And nor will you have a typical off-roader’s fuel bill to foot.

What’s more, the car on which it’s based is much underrated. The new version of the V70 is nowhere near as pretty as its predecessor – no, don’t laugh: it was a good-looking car – but it is hugely spacious with a boot big enough to stage a medium-sized air display. It’s nice to drive as well, in a quiet, softly softly sort of way.

Sadly, many of these attributes have been lost in the XC version. You can fiddle around with the suspension settings but no matter which button you press, the ride is never anything other than soft, with a hard and chewy centre. I didn’t like it at all.

I’m not sure either about the tough-looking body cladding, principally because I’m not sure it’s tough at all. I suspect it’s just something else to mend after a crash. And I wasn’t all that fussed about the engine. It was a 3.2 litre six, and while it wasn’t very bad, it wasn’t very good either. If it were a person, I suspect you wouldn’t invite it round for drinks because it would bore your friends.

The most worrying thing about this car, though, is who you’re buying it from. Ford, as we know, is thinking of selling Volvo, and I don’t know about you, but I wouldn’t pay nearly £36,000 to a car company if I didn’t know who was going to be running it next week.

In many ways the XC70 is a good car. It’s light and airy, well equipped and fitted with every safety feature known to man. It also meets a genuine demand – for a non off-road car that can do a bit of off-roading if asked.

But it doesn’t quite work. As a result, unless I really needed the Volvo’s vast boot, I’d save myself £14,000 and buy a Subaru Legacy Outback.

Vital statistics

Model Volvo XC70 SE Sport
Engine 3192cc, six cylinders
Power 235bhp @ 6200rpm
Torque 236 lb ft @ 3200rpm
Transmission Six-speed manual
Fuel 24.8mpg (combined cycle)
CO2 272g/km
Acceleration 0-60mph: 8.1sec
Top speed 134mph
Price £35,700
Rating
Verdict Not bad, not good, too costly

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