Road Test: Audi A6 S6 4dr Auto

With a V10 from a Lambo Gallardo, the last S6 should've been the ultimate Q car (that's ‘Q' as in ‘Q-ship', the normal-looking boats packed with secret firepower to ambush enemy subs). Except it wasn't. Sure, it hid massive speed under anonymous styling, but the engine was choked by an otherwise lifeless experience. This time, the 5.2-litre V10 has been binned, swapped for a 4.0-litre, 420bhp V8, found in 500bhp form in the new Bentley Conti GT.

The A6 range has been recently and wholly redone, with a lighter chassis and better handling to edge it closer to the 5-Series, plus entertainment systems with optional WiFi and satnav maps laid over Google Earth images. The S6 gets the same treatment, adding new alloys, silver wing mirrors and generally more lavish equipment such as noise-cancellation tech, which records background cabin sounds through mics in the roof, picks out the bad bits - like windrush - then cancels them by playing an opposite soundwave back through the stereo.

It's all very cultured. But despite a 0-62mph time of 4.6 seconds, it never feels explosive. The anti-noise tech works a bit too well, insulating you from the signs that you're travelling at potentially massive speed. The adaptive air suspension is incredibly comfortable, and the V8 is muffled, like you're listening to it with earplugs in. Must be the twin turbos, mellowing the mechanical anger. Push through an initial stickiness in the throttle/steering/brakes, and it starts to liven up, but it never feels hugely crisp or immediate.

This isn't supposed to be an especially racy car, but you can't help feeling it's a bit too subdued. It's an unarguably lovely thing to sit in, and the new materials and cabin tech have upped the everyday-premium game to new levels. But the refinements fight against the performance. For those who can't bring themselves to own a fast diesel, it has a fairly unique appeal. But if you're expecting a more liveable, muted version of the RS6 - or even an M5 - prepare for disappointment.