7

BMW gave its 6 Series a mild makeover for 2015. As most of the changes cover styling tweaks and equipment upgrades to the standard versions, spotting a new M6 Convertible requires a ‘Where’s Wally?'-type forensic eye.

There are small differences, though. Now you get LED headlights as standard, plus a gloss black finish around the climate control buttons to enhance what was already a beautifully crafted interior.

Power from the 4.4-litre twin-turbocharged V8 remains the same at 552bhp, however, someone must have written to BMW complaining that wasn’t good enough because M Division has also introduced a 592bhp Competition Package as well.

There aren’t many cars equipped with the Compeition Pack in the UK yet, so we made do with the standard car. ‘Made do’ perhaps isn’t the correct turn of phrase; even in this state of tune the M6 Convertible is still ridiculously quick and blessed with a great engine.

Step hard on the accelerator and there is a momentary pause while you wait for the two turbos to limber up. But when they do, cramming as much oxygen into those eight combustion chambers as each will reasonably endure, the M6 presses you firmly back in your seat and just goes.

So much so, in fact, that you'll do the occasional double take after contemplating the incongruous speed reading being beamed back at you from the head-up display. At this stage, you might utter something impolite, too.

It also sounds great, and all the better with the roof down. It’s not a lazy V8 burble, but a hard-edged, clearly defined howl, punctuated by loud woofs during each gear change. Those changes are finger-click fast, too if you set the seven-speed dual-clutch gearbox to maximum attack.

So there’s no questioning the M6 Convertible’s straight-line credentials, but eventually, inevitably, you will reach a corner. In this instance, your first task will be to shed speed, and suddenly you become aware of the car's two-tonne mass and the resulting inertia.

The huge discs and calipers scrub off speed well, but even so, you sense their struggle against that substantial bulk. The fact that the pedal has a longish travel and little feel doesn’t help inspire confidence, either.

As you turn in, no matter what driving mode you’ve selected, the M6’s numb-feeling steering wheel takes a few degrees to load up, which diverts some of your focus away from the corner itself.

All that weight makes it reluctant to make quick direction changes, too, but the M6 does generate enormous grip, so you can still carry plenty of speed into corners. And for a car of this size and power it’s very docile, with a tendency for progressive understeer at the limit. That said, switch off the traction control and it’ll transform into a drift car no problem.

However, if you dial all the driving modes back to Comfort and simply go for a cruise, the M6 Convertible will happily oblige. With the roof up the cabin is almost as quiet as that of the Coupé, while with the roof down and the wind deflector in place there’s not much buffeting, either.

The ride is harsh over really scarred roads, which diminishes the BMW’s grand tourer credentials, but in the main it’s tolerable. The rear-view mirror also shakes over lumpy surfaces - a telltale pointing to the loss of torsional rigidity that results from cutting off a long car's roof.

Backing off also leaves you time to enjoy that fabulous interior. It’s so well finished with swathes of leather and strips of carbonfibre that it’s no wonder the new gloss black fascia was all BMW could come up with by way of improvement.

It is also superbly equipped, away from the M Division tweaks and developed exterior, there is a real sense of class inside. There are still loads of M6 badging details throughout the interior so as not to forget you are driving a brute, not just a Grand Tourer, but there is also a Harman and Kardon stereo and an iDrive system featuring sat nav, DAB, Bluetooth, an USB interface and a 10.2in screen.

Overall, the BMW M6 Convertible is an odd car whose purpose is difficult to define. On the one hand, it’s hugely fast, but really it’s too heavy and the steering is too vague for it to feel like a proper open-top sports car. Equally, it has a wonderful interior but the ride is never compliant enough for it to be a proper GT.

As a result, if you want a car that serves one of these extremes, this probably isn't the car for you. Even if you can accept its betwixt and between nature, logically you'd be better off buying the still fast but cheaper to run 640d Convertible instead, if a luxury open-top is what you're after.

BMW M6 Convertible

Price £97,300; Engine V8, 4395cc, twin-turbocharged, petrol; Power 552bhp at 6000rpm; Torque 502lb ft at 1500rpm; Gearbox seven-speed dual-clutch automatic; Kerb weight 2055kg; Top speed 155mph (limited); 0-62mph 4.3sec; Economy 27.7mpg (combined); CO2/tax band 239g/km, 37%

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