See BMW’s new 645Ci in profile and you’ll discover something extraordinary. Look at the front of the car and you’ll think it’s a Volvo. Look at the back and it’s a Peugeot; rest your eyes on the bit in between the two and it’s pure Porsche 911.

The car is a visual schizophrenic and though it is neither ugly like BMW’s 7-series, nor awkward like the new 5-series, to those who remember BMW’s last 6-series, the achingly graceful model that bowed out in 1989, it is more than a touch disappointing.

This is a great shame, for these conflicting looks mask a car of considerable ability and one that puts to rest the spectre of BMW’s last big coupé, the unloved 1990s 8-series.

Ah, yes. The 8-series. When BMW presented the new 6-series it showed us a little film that dwelt lovingly on all the beautiful coupés of its past. And then, right at the end, there was the 850i, brought on like a bastard son in a cameo of the blink-and-you’ll-miss it variety.

Helmut Panke, the BMW chairman, admits now that BMW got the 8-series wrong, and the night before I drove the new 6-series he promised me the new car would be as good to drive as its old namesake. BMW’s big coupé would no longer be a boulevard cruiser but a hard-driving sports car. Looking at it, I couldn’t quite see it myself.

Then I drove it. At first I warmed to it to no great degree. It was clearly a mightily effective car, as quick as its 333bhp engine and 0-62mph dash in 5.6sec suggested. It rode very well and was sufficiently if not exceptionally quiet.

But of the old thrills I saw no sign. I had some of the best drives of my life in a 1988 M635CSi yet every time I tried to push its alleged successor, lights started flashing urgently on the dashboard as the car effectively took control, killing the throttle and hitting the brakes to keep the apparent lunatic behind the wheel from killing himself.

Happily, BMW — unlike some other car manufacturers I could mention — allows you to turn off the nanny state, and with both its dynamic stability control and traction control systems disabled the car was transformed for the better. I discovered these systems were programmed to cut in long before the car even reached its limit of adhesion, let alone stepped over it, so once unfettered from their unwelcome attention the 645 was not only a great deal more fun, it was a sight quicker, too.

Only then did I realise what a superb job BMW has done with this car. It’s a real driver’s machine: you can slide it around in slow corners, if that’s what you really want to do, but it’s at its absolute best hammering through really quick curves. I cannot think of another car that rides this well that can match its body control and stability in such circumstances.

Inside it’s very smart, restrained and comfortable. Indeed, the driving environment is spoilt only by BMW’s improved, refined but still infernal iDrive control system. One of BMW’s electronics experts told me that it was now as good as it was likely to get and, when rival systems such as Audi’s MMI exist, that’s not nearly good enough.

You’ll squeeze a couple of kids in the back of the 645Ci and if they’re under 10 they would probably be happy there over reasonable distances but it remains a 2+2 rather than a full four-seater. Given that, the boot — with its small aperture and unremarkable dimensions — will probably prove big enough, just, for a carefully packed family holiday.

It’s hard to think of competitors for the 645Ci. The Mercedes CL is too big, expensive and staid, while Jaguar’s still endearing XKR is old and utterly outclassed by comparison. A Maserati coupé is an interesting emotional alternative — though, engine aside, any objective assessment would leave it just as surely on the sidelines.

Which means the 645Ci is exactly where BMW wants it: in a niche pretty much of its own making.

A convertible will have arrived by the time sales begin in March, though its roof will be canvas, not steel like the Mercedes SL and, unlike its rival, it will retain its rear seats, albeit in even more cramped quarters. Cheaper versions are likely to be announced in the next year: either a V8-powered 635Ci or a six-cylinder 630Ci, while early in 2005 a 500bhp, V10-powered M6 will hit the headlines. Customers who remove its speed limiter will discover they are owners of a 200mph car.

In the meantime the 645Ci seems likely to delight all those who buy it. It’s not an attractive car but, sadly, this should no longer surprise us from BMW. Perhaps a coupé is the one car you should be able to judge from its cover, and the fact that its appearance so betrays its abilities is its single biggest failing. The car inside is better by far than it looks.

VITAL STATISTICS

Model: BMW 645Ci
Engine type: V8, 4398cc
Power/Torque: 333bhp @ 6100rpm / 332 lb ft @ 3600rpm
Transmission: Six-speed manual or automatic, rear-wheel drive
Suspension: (front) MacPherson struts, coil springs, anti-roll bar (rear) Multi-link rear axle, coil spring, anti-roll bar
Fuel/CO2: 25.9mpg (combined) / 264g/km
Acceleration: 0 to 62mph: 5.6sec
Top speed: 155mph
Price: £49,855
Verdict: Looks ugly, drives beautifully

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