But before we get to the nitty-gritty I'll remind you of the RS4's vital statistics. The car goes on sale in January at ΂£49,980, which is a lot for an Audi A4 and substantially more expensive than the superb M3 CS (΂£43,555). However, delve a little deeper and it doesn't look like bad value at all.

The RS4's crowning glory is undoubtedly its S4-derived direct petrol injection 4.2-litre V8. It's hugely powerful, as you'd expect of an RS-model Audi, but there has been a clear shift in philosophy. Where you might expect twin turbos and quite a lazy delivery, you instead find normal aspiration and a rev limit of 8250rpm. Peak power of 414bhp is produced at a heady 7800rpm, and even the torque peak of 317lb ft doesn't arrive until 5500rpm.

Don't be fooled, though. Ninety per cent of that is available from as low as 2250rpm and remains on tap up to 7600rpm. The V8 is a bit of a screamer, but there's also the promise of big-hearted thump when you really need it. When you can use all the revs, the RS4 will leap to 62mph in a claimed 4.8sec, but the killer figure is its 0-124mph time of just 16.6. That's not too far behind a BMW M5...

The power is harnessed by Audi's quattro permanent four-wheel-drive system, but again expectations are confounded when you learn that for the first time the drivetrain delivers more power to the rear wheels than the fronts. With 60 per cent of the torque sent aft, and as much as 85 per cent directed there should understeer set in, the RS4 could just be the hot Audi we've always craved.

It looks fantastic: muscular and aggressive but with a sophisticated restraint. Audi and Quattro Gmbh do this sort of thing better than anybody. The interior's pretty special, too. The winged Recaro seAats lift an already stylish and beautifully constructed interior, and the flat-bottomed steering wheel is an unashamedly sporting finishing touch. Shame the polished 'metal' segment feels cheap.

Twist the key to prime the engine, then depress the starter button located next to the handbrake and the V8 catches instantly and bursts into life with a spirited flourish. It's not difficult to spot the engine's configuration, but there's a sort of pared-down tightness to the note. There's no waste, and perhaps this is naίve, but the sound seems genuine. And you just know it wants to rev.

Hit the 'S' button on the left steering wheel spoke and you engage Sport mode. Throttle response is quicker, the side bolsters of those seats inflate to suck you into their embrace and a trick exhaust valve opens to give you even more sound. See, told you this was a bit special...

Of course, all this detail will mean nothing if the RS4 doesn't deliver on the sort of roads that an M3 CS would devour in great chunks. First impressions are encouraging. The gearshift has a delicious precision to it and a genuinely short throw, the Servotronic steering is a shade too light but has none of the finger-twirling slack of cooking A4s, and the ride on the chunky 19in alloys is excellent. The engine isn't quite what you expect, though. The sheer grunt available from as little as 2000rpm might lead you to believe that Quattro Gmbh had secreted a couple of turbos under the bonnet after all... It really is a league above an M3 in terms of neck-straining punch from low speeds. No wonder the press pack lists cars as diverse as the Carrera S and Mercedes E55 AMG as rivals.

When Milan's urban crawl gives way to narrow and ferociously testing switchback roads, that low-end torque is essential to fire the RS4 out of tight hairpins. Get on the power too early and the RS4 scrubs into understeer in much the same way that any Audi would, but with a bit more patience the RS4 starts to make sense. Turn-in and wait just a fraction of a second for the front tyres to get a purchase on the surface and it'll take full power with no problem, and as the corner opens out the rear can even be coaxed into a gentle slide.

Quicker corners reveal that the RS4 has excellent turn-in, while the overall feel is light and responsive; you'd struggle to spot that the V8 was slung-out ahead of the front wheels. Steering feel isn't Porsche-quality but there's a consistency to the weighting that Audis have often struggled to capture (although the front-drive A4 DTM is pretty good in this respect, too). Similarly, the brakes have a subtlety and progression that previous RS models have desperately needed. Stopping power is exceptional, as you'd expect of 365mm front discs clamped by eight-piston four-pad callipers, and even after countless stops for first-gear hairpins, fade was notable by its absence.

Audi's 'DRC' (Dynamic Ride Control) suspension system, first seen on the RS6, ensures body control is a match for the stupendous performance. The system connects diagonally opposed dampers with a flow of oil and a central valve. At low speeds the valve stays open to ensure optimum ride quality, but when the car rolls or pitches the valve starts to close, exerting pressure on the oil, which forces the damper to push back on the spring and reduce the angle of roll or pitch.

It's a neat and lightweight system compared with more complex electronic damping systems employed by the likes of Mercedes, and it certainly keeps the RS4's weight in check. There's not a great deal of roll and the angle that's adopted feels natural rather than synthesised. Even rapid direction changes are executed in a measured, calm and precise movement. Stability is the RS4's overwhelming quality.

Which, as you may have guessed, means that the RS4 is no tail-out hooligan. Keep your finger on the ESP button for a few seconds to dial-out the two-stage stability programme (a short prod removes traction control only), and the RS4 doesn't suddenly morph into an infinitely adjustable drivers' tool. However, it's less doggedly understeery than Audis of old, and through quicker corners you can use a lift on turn-in to bring the rear of the car into play and keep the RS4 neutral and driving hard through the turn. It rewards a committed style, and when you do use the RS4's full arsenal of power, braking, grip and traction, it's devastatingly rapid. An M3 driver wouldn't stay in touch for long on an unfamiliar road.

Essentially the RS4 is the natural progression for Audi's ultimate performance cars. It's still hugely fast, unerringly secure and impeccably built. But it's in the detail that it really moves things on, from the weighting of the steering to the quality of brake feel and the simply awesome delivery of the V8. You feel more involved, more inclined to really work the RS4 to its limits. And when you do it retains its composure for longer, feels agile rather than just steamrollering the road surface. It's a triumph for Audi and Quattro Gmbh and, against the odds, a genuinely entertaining alternative to an M3.