Sector: Compact Executive Price: £55,525 Fuel: 26.4mpg CO2: 249g/km

As usable and, in some cases, as practical as the modern supercar has become, there’s something really special about dressing one up as a family car. The Audi RS4 manages almost everything you could demand from the A4 Avant, but with the heart of an R8 under the bonnet it’ll do much more besides.

Audi has been serving up fast estate cars for 19 years, starting with the part-Porsche RS2 Avant and branching out to the RS4 and RS6 we’re familiar with today. In each case, the formula is fairly simple, using a large engine and the brand’s quattro four-wheel drive system.

Not very fleety, I hear you cry. There will of course be a lucky few who can use this as a business vehicle, but the RS4’s value goes further. With its big wheels, aggressive bodykit and carbon fibre-drenched sports interior, it’s a halo for the diesel A4 Avant and likely to sway drivers to tick a few extra boxes on the options list. Big wheels? Check. S line? Yes please.

Following the last two generations, it’s taken until the facelift for Audi to bulk up its compact executive estate car. The result is subtle but purposeful, with robust-looking 19-inch wheels tucked under arches that look like they’ve been borrowed from the original quattro coupe. It has a commanding on-road presence, but it takes a knowledgeable passer-by to really know what it is.

Under the bonnet is an R8-derived 4.2-litre, as used in the RS5, paired with quattro four-wheel drive and a seven-speed dual-clutch gearbox. There are no turbos, no superchargers and there’s no option to change gears yourself, unlike the BMW M3. But you do get a fantastic soundtrack. That 444bhp engine barks into life from cold, steadily settling to a crackly metallic roar at idle.

It’s a thoroughbred Q car, with two distinct personalities. The RS4 is effortlessly fast in a straight line, with grip limits you’d struggle to exploit on anything other than wet roads. But it’s also as spacious as any A4 Avant, comfortable and at 26mpg on motorway trips it’s not painfully uneconomical either, though its 61-litre tank only lasts around 300 miles.

Comfort mode makes the suspension soft and the engine quiet, it’s far from sluggish but the gearbox hunts for the highest possible gear and the throttle and steering numb up, with a reluctance to shift down unless it’s 100% necessary. There’s so much power here that it usually isn’t. The trouble is, that soft suspension and an 1,800kg kerb weight makes it slightly too wallowy.

Dynamic is the polar opposite, sharpening everything and making the exhaust noticeably more vocal, adding a bark to every gearchange as it matches the revs and firming the suspension so much that it’s really only glass-smooth tracks and Continental motorways that won’t feel almost instantly tiresome. A middle-ground Normal setting would’ve been welcome for our crater-filled British roads.

It can also leave the car feeling a bit anonymous. The A4 is a cornerstone of the UK fleet market, and a ubiquitous part of our motorway network with plenty of drivers opting for the S line trim. Stuck in traffic, the interior isn’t quite enough of a departure from a well-specced S line to feel like a car at this price bracket.

But then, with its true performance potential so neatly hidden away, perhaps that’s the point?

Verdict:

A supercar dressed as a practical family estate, the RS4 has its own character against the saloon and coupe-only M3 and rear-wheel drive C63 AMG. It’s excellent fun, but you’ll need an Autobahn or a track to really find out what it can do.

Watch the latest video of the Audi RS4 Avant