Belting along a gloriously smooth mountain road in 35C of blistering South African sunshine and part-wrapped in a 400bhp+, turbocharged, rear-wheel-drive V8 convertible, you'd think things couldn't get any better.

The sky is an impossible cobalt blue, and red-gold rocks rise to one side peppered with stubby, uncomfortable-looking shrubberies, while a rocky, light-swallowing gorge falls precipitously away on the other.

Random jaywalking baboons add a frisson of red-buttocked expectation to every blind apex. I'm in a rapid car picking idly away at the frayed edges of my comfort zone and getting ever-so-slightly faster into every corner. I should be in my element. Except I'm not.

Because the new BMW 6 Series Convertible is boring.

Which is definitely not the same as saying that the new Six is a bad car, so this is going to take a bit of explaining.

For a start, the new version of the 6 Series Convertible - we'll get the Coupe later in the year and a 'four-door coupe' in 2012 - certainly looks less divisive than the previous generation, having grown a long horizontal swage that carries through the bootline, thus neatly killing the last version's polarising prodigious arse.

It has a nice-looking canvas roof, a lovely interior, goes around a corner and stops well and regularly. When given sufficient cause, it also understeers just enough to let you know you've reached the end of playtime.

A dynamic statement immediately contradicted by a swing of oversteer if you binge on the throttle halfway round a corner having previously sedated some of the myriad stability and traction control options.

The body is well-controlled, the active damping is firm but usable - this is a very smooth road - and the engine has over 440lb ft of flex.

And yet the new 6Series seems to be a lightning rod for joy. It's like driving around in a Laura Ashley console table; you may be aware that it's well-made and expensive, but everything has been so very obsessively aimed down the middle of the road that it registers exactly nil for surprise and delight.

It matters more because this should be an exciting car from BMW. The serious stuff goes like this: from launch, there will be two engines, both petrol. We'll get the 640i and 650i, the 640i a 3.0-litre TwinPower bi-turbocharged straight-six, the 650i a similarly twin-turbocharged 4.4-litre V8. So, lesson one, you can't trust anybody's badges to tell you what's under the bonnet.

Which makes everything trickier to remember, but scores bonus AutoGeek' points against motoring novices. The 640i - which is a 3.0-litre, don't forget - shoves out 320bhp and 332lb ft of torque, hits 100km/h in 5.7secs and a limited 250km/h.

It makes peak power at a relatively low 5,800rpm, so this is no operatic BMW six, but despite the respectable figures, it produces just 185g/km and manages nearly 36mpg on the combined cycle, meaning that for what it lacks in tingle-range, it makes up for in blunt grunt and day-to-day efficiency, helped along by standard-fit stop/start.

Putting all that aside, we're not really interested in the 640i. And not only because there were none available to drive at the launch (though I freely admit this might have something to do with it).

Let's be thoroughly honest with each other: if you're going to go petrol, go big, and until the M6 version turns up with 580-odd bhp, we'll have to make do with the only mildly whopping 650i.

Now bear in mind that this is the same 4.4-litre bi-turbo due to see duty in that M6, the forthcoming M5, and already sees active service in SUV Xs 6M and 5M, detuned a bit and rejigged for cruise rather than bruise.

So on paper, it's a belter: 407bhp, 443lb ft, 100km/h in five dead and the standard 155mph electronic guardrail. It will also crack 26.4mpg on the combined cycle and emit just 249g/km - which is going some for an eight-cylinder with a pair of turbos nestled in its cylinder cleavage.

Both come with a standard-fit eight-speed automatic - due for introduction to the 1-Series range, oddly - a gearbox that, despite carrying a couple of spare ratios around apparently for the hell of it, nevertheless constantly impresses, both in terms of shift quality and speed.

It really does do both town loitering and responsive-enough paddle-shifting. It's not necessarily a sporting gearbox, but its breadth of ability is very satisfying.

Satisfying, because when poked, the 650i can really move. All that torque liberally smeared across the bottom-end, and the car veritably leaps off the line, and then bullishly revs to it.

On the mountain roads near Franschhoek, up the R321 from Somerset West, it's possible to find yourself settled into a very brisk cadence.

Switching between two gears of whose numeral I was blissfully unaware (though I suspect it was third and fourth), the Six fairly flew along, reaching eye-widening speeds with licence-losing ease. Everything reliable and predictable as the finest industrial machinery always is.

But the engine doesn't sing. It bellows in the lower reaches, burps up a guttural pop between quick gearchanges like a DSG and sounds like it might open up, but then tails off. The power is broad-shouldered and thrusty, but the convertible weighs in excess of two tonnes, so the grunt never seems given freely.

Fact is, the whole car feels filtered. Look away now if you get irritated by unavailing manufacturer specifications, because the 6 Series has been tattooed with every bauble and glitteringly pointless acronym that BMW can provide.

As standard in the UK we'll get DSC-Plus and PDC (Park Distance Control) as well as the usual leather and xenons, but you can option Integral Active Steering, Adaptive Drive (dampers), side-view cameras, a head-up display, reversing assist with top view, active cruise with Stop and Go, lane-departure warning and speed-limit info.

There is, inexplicably, more. But I fear that you'd die of boredom. The glorious irony being that Active everything conspires to make the 650i fast without being gratifying.

For instance, the steering remains a major bugbear. Standard steering will now be via EPS (electric power steering), and even though the system extorts far less energy from the car to work than a hydraulic set-up, it does precisely nothing for BMW's reputation as a driver's car.

Yes, it's accurate - the car goes where you point the wheel - but the car TG drove, complete with the Active Steering variable-ratio rack, felt, frankly, a bit bizarre.

The car is lower (by 9mm), wider (by 39mm), and longer (by 74mm - most of that in the wheelbase),than the model it replaces, also coming up wider in the actual track and wheelbase than the outgoing Six convertible.

Compared to the old car, the new structure is now around 50 per cent stiffer in terms of torsional rigidity (if you were to try to corkscrew the bodyshell, a car's torsional rigidity is how it passively resists that kind of movement), and in the interest of weight distribution, the doors, bonnet and front axle spring mounts are made of aluminium.

Interestingly, BMW seems inordinately concerned about the new 6's slight podginess: the front side panels, roof stowage compartment lid and boot are all made from 'glass-fibre composite' in an attempt to at least scrape into BMW's Efficient Dynamics embrace.

You can immediately feel how much time has been spent honing, tweaking and perfecting. You'll still find a shimmy on poorly surfaced roads, but that's probably down to a suspension set-up on the far side of firm unless the surface is glassy. The roof drops quite quickly and neatly (19 seconds), raises slightly less swiftly (24), both operations possible up to 25mph.

There's a usable boot, though possibly not enough for much more than handbags for the eminently possible quartet of occupants. The interior, with all instruments canted a couple of degrees towards the driver and an intriguing semi-m??bius twist through the centre console, is both Teutonically perfect in execution and simple to actually use.

Roof up, it's quiet on the motorway, cosy and pleasing, though there's a huge fabric fin buttress obliterating the rear vision, and roof-down, it's unflustered and all but silent, especially if you have the optional wind-deflector in place. Tot up the points, and the Six Convertible is a winner.

But the problem with the 6-Series, as a convertible at least, is that it's so aggressively competent, it fails to have a touch-point. It seems as if too many opinions have been asked in the making, so that it has become a car born of committee rather than singular vision.

There's an erosion of will that gently laps at your thought process: the Six is so glossy and slick that there's actually nothing on which to get any emotional traction.

There's nothing here that actively offends, and yet there is also a remarkable lack of any reason to buy the car, unless you value relentless competency over all other factors.

In a world of statement cars, the only statement the new 6 Series convertible apparently makes about you is that you aspire to be a successful Floridian dentist. Not a bad choice, just the wrong one.

Tom Ford

We like: BMW's anal attention to detail
We don't like: Precious little to get excited about
TopGear verdict: A beautifully built, efficiently designed convertible. But expensive and a touch dull.
Performance: 0-62mph in 5.0secs, max 155mph, 26.4mpg
Tech: 4395cc, V8, RWD, 407bhp, 443lb ft, 2025kg, 249g/km CO2
Tick this on the options list: Comfort seats, EU1,485; HUD, EU980
And avoid this: Night Vision, EU1,535