HERE'S a telling way of figuring out who (as well as what) exactly BMW was aiming for with its respective 6 Series coupe and convertible.

If you open the boot and then stand back to admire the profile, its resulting fastback look is uncannily Porsche 996 911.

But there’s more. Roof-up and rear-on, and the convertible’s flying buttress window fins are pure Jaguar XJS, one of the automotive world’s archetypical grand tourers.

And so it came to pass, even on the fantasy racetrack test route a small number of assembled journalists were allowed on to put the dynamic duo through their paces.

Make no mistake. Even at 1620kg, the automatic 645Ci coupe is a real sports car, with a tremendous amount of performance, handling, grip and braking on offer.

Acceleration is outstanding, with a seamless supply of revs all too ready to hit the limiter. Yet the engine sound this makes getting there is heavenly, more akin to a motorised Bach than bark.

Any doubts about the stability, control and feel of the Active Steering at high speed are unfounded, with a weighty alacrity to the 645Ci coupe’s handling and cornering abilities that totally belies its substantial size and weight.

It’s staggering how you can sense the road surface and know exactly the amount of steering input to dial in, in a car that’s varying the degrees of wheel-twirling necessary. The steering’s rock solid and comes through loud and clear.

Unlike the undesirables that usually sort the GTs from the DTs: there’s no rack rattle, track shimmying, undue road roar, wind noise or mechanical mayhem coming in at any speed, let alone at close to 200km/h. You’re comfortable, cosseted and secure but also in control here.

The six-speed automatic probably better suits the Six’s sport/luxury dual personality, with its regular ‘D’, ‘DS’ sport mode or ‘M’ Steptronic tip-shift options offering something for everybody – especially when the ‘Sport’ mode added a measured improvement in steering and performance response.

In contrast, the six-speed manual sampled felt fine but maybe required a little too much effort and concentration on the race track after the virtually as-quick auto. And you’re more conscious of driving a large rear-drive V8 with the stick-shift, while the self-shifter shrinks around you by comparison.

Meanwhile, the 200kg heavier 645Ci convertible is a significantly different car, with its slightly softer and more hedonistic agenda.

The extra weight seems to blot out even more road irregularities than the less corpulent coupe, but the flipside is you can feel it in the ragtop’s blunted performance. It’s still brutally fast though.

An odd upshot of the added bulk around the track’s slalom course was the convertible’s slightly more planted feel, but this is obviously dependent on the speed the curves were taken at.

Overall, the convertible is still very much the seriously capable sports luxury coupe. And it offers the benefit of stadium surround sound when the engine’s revs are rocketing skywards and the roof is down. Impressively, at these high speeds all is pretty calm and composed inside, so refinement levels are as high as the deliriously punch-drunk happy driver.

Cabin presentation is what you’d expect from BMW, with the added interest and intrigue of the now intuitive i-Drive device.

There seems to be nothing lacking or amiss in the luxury stakes for the money, while the compromises endured by rear-seated adults are not as bad as one might imagine.

Which brings me back to the styling.

Brave design deserves time as well as respect. Nobody today questions the validity of futurist vanguards like the 1955 Citroen DS, 1967 NSU Ro80 or even the 1990 Toyota Tarago (nee Previa), but they – like the latest BMWs – initially raised eyebrows as well as challenged convention.

The 6 Series, despite its 911-esque tail when the boot is open, is peppered with interesting detailing draped over lovely proportions. It has pure presence and forces you to think. And that’s a breath of much-needed fresh air.

But the real beauty of the 645Ci is that it leads in many other ways too.

Porsche, Mercedes, Maserati, Lexus and Jaguar have a formidable foe on their hands.