A convertible M6 is a mish-mash of goodies that should combine to create a foul-tasting mess: one of the finest performance cars in the known world and a top down boulevard cruiser of the highest order.

Open top motoring in style

Some things, technically, should not work together. Bacon-flavoured ice cream was a recent triumph over adversity that should be used to make children sick up poison, but in fact won a Chef a Michelin star in Britain. And that bizarre meal sprung to mind during every scrumptious mile in the BMW M6 Cabriolet.

A convertible M6 is a mish-mash of goodies that should combine to create a foul-tasting mess: one of the finest performance cars in the known world and a top down boulevard cruiser of the highest order. It takes a brave soul to put them in the same package because chopping the roof off is one of the simplest ways to ruin a car. Especially when BMW went to such lengths to keep the pounds off the M6’s hips in the first place.

Remember the hard-top comes with a carbon-fibre roof and a plastic boot? They were sheer essentials at the time. Now they’ve been replaced with a mechanical folding roof that adds a disastrous sounding 220kg to the final kerbweight – which means this car now tips the scales at almost two tonnes.

So it should handle like a bag of wet cement, it should have us decrying BMW’s act of vandalism across the Seven Seas. If you added the weight of three fat girls to a Ferrari it would feel like it had run over a Stinger, so of course it would kill the Roundel stone dead.

But the big BMW is different, because these uber M-cars aren’t really sports cars and never were – not in the traditional sense. Yes the M6 and the M5 before it was supercar fast, but they never relied on a driving virtuoso pulling every last ounce of the chassis’ performance through their fingertips at the apex. They were all about bone-pulverising acceleration and a raft of technology holding things together and hiding the weight like a master tailor in the corners. Losing the roof doesn’t really change that basic ethos.

And it is slower, there’s no hiding that. The big barge now takes 4.8s to hit 60mph, rather than the 4.6s for the lighter hard top, and will probably take two whole seconds more to get to the limited top end of 155mph. Which sounds quite a lot, for about 0.2s.

See it is a lot on a racing circuit, but nothing at all when pulling gently away from traffic lights on the Cote d’Azur or even hammering down round winding roads as fast as the biggest faultline in the whole car, the organic matter behind the wheel, thinks the car can go.

It would take a prison-grade psychopath endowed with a racing driver’s skill to push this car to the point that you’ll feel a real difference on the public roads. Yes the traction control might kick in a millisecond earlier on a hairpin bend, yes you might lose a gnat’s whisker in tyre scrub thanks to the extra weight. But the kind of person that buys this car simply won’t know or care.

And the payoff is more than decent, as the sound of that monster V10 without that extra layer of padding is one of those things that will stay with you forever. This 507bhp 5-litre was a revolution rivalled only by sliced bread just a couple of years ago. Now so much has been written there is no need to rehash the world of bedplate design, individual butterflies and more. It’s been done twice before and it’s the same V10: suffice to say it’s a technical masterpiece.

And while reading about it time and again may send you cold, the view from the driver’s seat is a whole new story every time – even in Winter. It’s still fascinating how this car sounds like a diesel on start-up, can tootle along with a ‘mere’ 400bhp at its disposal and yet, at the touch of a button, unleash the dogs of war and hang with a Gallardo or F430. And now there’s wind rushing past your face, which makes it feel even faster.

It was loud enough before, too, but fully exposed to the elements with the needle homing in on the 8000rpm redline was as close to a spiritual moment as an executive roadster should be able to provide – the traction control light blipping gently to prove there really was that much power and the Heads-Up Display reminding me that this test was in Britain and I could go to jail.

And it did it all with neat touches like the deflector screen that kept us snug, a ride that had somehow been saved by the same computers that stopped the handling falling apart. The M6 Cabriolet did it all in style.

Of course the seven-speed sequential is there in full-effect, and still feels a little too clever for its own good. With 11 different settings for the ‘box alone, before you get to the traction control, seat bolsters and more, it feels like you’d spend forever chasing the perfect set-up in this machine. But again, those that buy them won’t give a damn, and in any case the wheel-mounted M Button drops it to its sportiest settings in a heartbeat.

Still I couldn’t buy one. I don’t have the whopping £86,340 it will cost or the patience to explain to pedantic idiots like me that the losses really aren’t that bad and the advantages of top-down motoring more than compensate for that 0.5s lost on a lap of Hockenheim, which my car would never do in any case.

But much to my own chagrin I loved this smoke and mirrors exercise to extract funds from cash-heavy bankers. The BMW M6 Cabriolet truly is bacon-flavoured ice cream and, while I hate to admit it, tastes mighty fine.

Gallery: WCF Test Drive: BMW M6 Cabriolet