The Audi RS5 Cabriolet is a new hardcore version of the company's elegant four-seater soft-top.
To all intents and purposes, it's a direct rival for the BMW M3 Convertible. However, with a starting price of 68,960, Audi's take on the drop-top dragster costs 7300 more than BMW's.
The RS5 does manage to outdo its German rival on power, though (444bhp plays 414bhp), and this helps it accelerate slightly faster. It's also marginally more efficient, managing average economy of 26.4mpg compared with the BMW's 24.6mpg.
A host of visual changes mark the RS5 out from lesser A5s, including 19-inch forged alloy wheels, flared wheelarches, a fixed carbon-finished rear spoiler and large oval tailpipes.
What's the 2013 Audi RS5 Cabriolet like to drive?
Exercise a heavy right foot and the RS5 digs in and bullets away from the mark.
Booming out a deep V8 bellow, it quickly shifts through its seven-speed automatic gearbox, making full use of its traction-enhancing four-wheel-drive system.
The chassis is lowered by 20mm compared with the standard A5's and features heavier-duty suspension components to help it cope with the extra stresses.
There's also a torque vectoring system (this can distribute different amounts of torque to each individual wheel) and Audi's Drive Select, which lets the driver adjust the throttle sensitivity, gearshift speeds and steering weighting.??
Our test car also had Dynamic Ride Control installed an option that allows you to vary the stiffness of the shock absorbers.
All this technology endows the RS5 with a huge amount of sideways grip and immense traction out of slow bends.
Unfortunately, it still takes a good deal of manhandling to get the front of the car to change direction; an M3 is far more agile. The RS5's steering isn't ideal, either, because the weight doesn't always arrive quickly enough, which can be unnerving when you turn into a bend at high speed.
Even more tellingly, it doesn't take much provocation with the brake pedal before the front suspension struggles to contain the transfer of weight, causing the tail to feel quite loose.
The trouble is, for all its clever technology, the RS5 is let down by the flawed chassis of the A5 Cabriolet. This also badly affects ride comfort; drive over any surface that isn't glassy smooth and tremors can be felt through the whole cabin as the suspension tries and fails to mask how much the flex there is in the body.
More positively, roof down and with the wind deflector up, turbulence is all but eliminated, leaving you free to enjoy the V8's baritone burble.
Then when you raise the powered, triple-layered roof (it takes 17 seconds and can be operated at up to 31mph) the Cabriolet becomes almost as civilised as a steel-top coupe.
What's the 2013 Audi RS5 Cabriolet like inside?
The cabin looks and feels seriously special. High-grade materials and smooth-operating switchgear predominate, although the RS5's MMI infotainment system is slightly clunky compared with the systems found in more modern Audis, such as the A3 and A6.??
Finishing touches include leather sports seats and a neat three-spoke, flat-bottom steering wheel with gearshift paddles.
Although there's plenty of room for the driver and front passenger, larger folk won't want to ride in the back for too long because leg- and headroom are on the tight side.
On the plus side, the Cabriolet's cloth roof gives it a distinct advantage over folding steel-roofed cars such as the M3 because it doesn't rob too much boot space when folded.
With the roof down, you lose just 60 litres, leaving 320 litres of available luggage space. Flip the rear seatbacks down and this grows to 750 litres with the roof in place.
Standard equipment is as generous as you'd expect given the near-70k price, and includes satellite-navigation, cruise and climate controls, xenon headlights and leather seats.
Should I buy one?
Unless you're desperate to be seen driving the ultimate A5 Cabriolet, the answer has to be no.
Yes, the RS5 delivers immense straight-line speed, but despite Audi's best efforts, the fundamentally flawed chassis struggles to cope with the engine's brutal power.
A BMW M3 Convertible isn't just significantly better to drive, it's also much cheaper to buy even with the optional DCT automatic gearbox installed.
Alternatively, you might be tempted to wait for the new BMW M4 Convertible, due to arrive in early 2014.
What Car? says...
Engine size 4.2-litre V8 petrol
Price from 68,985
Torque 317lb ft
0-62mph 4.9 seconds
Top speed 155mph (limited)
Fuel economy 26.4mpg
CO2 emissions 249g/km
By Pete Tullin and Will Nightingale