IN THIS FEATURE An air of restraint Brisk yet relentless A glint in its eye Fuel consumption could be a problem

Let's get right to the point here. The Audi S6 Avant is a flawed and compromised car, but despite its faults, it has a hugely seductive three-dimensional appeal. I walked away from the S6 after a day behind the wheel with a sharp sense of regret at our separation. I really like this car, but it took me a while to find out why.

I initially felt underwhelmed walking up to the S6. This third-generation S6 Avant is a particularly muted upgrade over the standard A6. You get the anticipated body kit, satin-finish wing mirrors and roof rails and a set of beautiful 19" tuning fork alloy wheels. Oh, and a pair of tiny V10 badges on the front flanks. But there's a distinct air of restraint about the whole package that's shared with the S6 saloon.

The S6 is relatively restrained

The S6 may look like any other sporting A6 to the untrained eye, but one feature sticks out. Below the headlamp units are a pair of always-on daylight driving lights. Each light contains five eye-squintingly bright light emitting diodes - one for each cylinder, see. They may have some safety value, but I couldn't help thinking they looked a bit chavvy.

Which all seems at odds with what sits beneath the S6's sheetmetal - a 5.2-litre all-alloy V10 derived from the Lamborghini Gallardo, that's also put into service in the S8. Except its not the flame-throwing, blood-spitting maniac you expect it to be. At idle it sounds bassy and muted and at low urban speeds it never ventures beyond a very faint offbeat growl. It's only as the rev-counter needle swings towards 7,000rpm that a crisp wail filters into the cabin. And even then it's hardly exciting enough to seek out tunnels for an open-window aural treat.