TG drives the new Audi RS5 Cabrio

What's this thing tailgating me at a distance of barely four inches?

It's Audi's new RS5 cabrio, arriving in the UK early next year to beat a frenzied assault on eardrums nationwide.

It's a bit noisy?

More than a bit. Piped through a dual-clutch gearbox and a fat pair of tailpipes, the RS5's 444bhp 4.2-litre V8 emits a mighty fanfare of booms, thumps and chunters, overlaid by a manic scream as the naturally aspirated engine reaches for its 8,500rpm redline. And, of course, with no roof to get in the way, all that noise is piped straight into your happy, gurning face. The RS5 might be the end of the line for non-forced-induction RS cars, and if it is, it's going out in a blaze of decibels.

I'm guessing it's not slow either?

You guess most correctly. The RS5 cab will do 0-62 in 4.9 seconds on its way to a top speed of 174mph - if you remove the 155mph limiter, which you obviously will. But it's not just the speed of the RS5, it's the way it goes about it, serving up an all-you-can-eat buffet of grip, traction and, er, even more grip.

Four-wheel drive, then?

But of course. This is a fast Audi, after all. The cabrio is more or less mechanically identical beneath the surface to the RS5 coupe, with a crown centre differential sending up to 85 per cent of torque to the rear wheels or 70 per cent to the front. In addition there's a sports diff across the rear axle, plus torque vectoring and optional adaptive damping working on diagonally opposed wheels. Complicated, clever stuff that all adds up to a phenomenally sure-footed car.

Not one for the opposite-lock enthusiast?

No. If you drive it like an absolute idiot, you can provoke it into moving around a fraction as the RS5 shifts its torque about in search of grip, but mainly it just serves up immutable traction. And grip. And traction.

Can't fast Audis sometimes be a bit... lumpy?

They can. We've never quite gelled with the RS5 coupe, finding it - though ballistically rapid - a bit distant and hard-riding. The cabrio, though hardly a wafty barge, seems just a margin more compliant. Maybe it was the tarmac of our test route - smoother than a freshly-shaven baby - or maybe it's just that, with your face under assault from the local insect population and your ears under assault from the RS5's exhaust, you're rather distracted from any bumps transmitted through the chassis. That said, the RS5 remains a trifle remote in terms of feedback: certainly less fingertip-engaging than, say, the BMW M3 cabrio.

But the M3's got a great folding-metal roof, hasn't it? Surely the RS5's lighter?

You'd think, wouldn't you? In fact, the Audi weighs in a few kilos heavier than the BMW, despite its lightweight fabric roof. It tips the scales at a beefy 1920kg, around 200kg more than the RS5 coupe, which might give you some idea how much bracing is required to stop a 444bhp cabrio twisting like a piece of fusilli in the corners.

It's no Lotus Exige, then?

No. Drive the RS5 hard and it's very apparent you're in control of a very big lump of metal going very fast: get hard on the brakes and you can sense a great deal of mass attempting to overtake you. Generally, though, the RS5 does a mighty impressive job of keeping all its bulk in check. Did I mention the whole 'relentless grip' thing?

Just a few times. So should I buy one?

Tricky one. With our sensible hats on, we'd concede that if you want a fast A5 cabrio, the S5 - with its 3.0-litre supercharged V6 - is as quick as you'd ever need, and you don't need to drive it so hard to get the most from it.

And with your sensible hats off?

Go for it. The RS5 cab is undoubtedly a more engaging proposition than the RS5 coupe, making the most of all that awesome V8 noise and overcoming its slightly po-faced driving dynamics through sheer sensory drama. The RS4 Avant remains our mid-size fast Audi of choice, but this is is the one for aural obsessives.

Any other convenient-yet-unrelated titbits that you've failed to crowbar into this review so far?

Glad you asked. This is just the start of 2013's hot Audi assault: celebrating the 30th anniversary of Quattro GMBH, Audi will introduce four RS models next year. Alongside this RS5 cab and the 553bhp RS6 Avant, we'll see a saloon RS6 and an RS version of the Q3, most likely sporting a 2.5-litre five-cylinder turbo serving up around 335bhp. Get ready for the RSUV invasion...

Sam Philip