With its powerful yet refined V8, Audi's flagship Q7 sets a new performance benchmark in the luxury SUV class. While it's not the most capable off road, the seven-seater is very quick, and offers fine handling and rewarding road manners, too. Only firm suspension lets the chassis down. The £4,000 stereo system is another highlight. With a total of 14 speakers, it sounds every bit as expensive as it actually is!

Since it was launched 13 months ago, the Audi Q7 has proved that bigger is still better when it comes to 4x4s. More than 88,000 have rolled off the production line so far.

To drive the success story on even further, Audi has now given it the most powerful diesel on the market. The 4.2-litre V8 has 326bhp and 760Nm, and propels the two-and-a-half-ton Q7 from 0-62mph in 6.4 seconds.

On the road, this performance is made all the more incredible by the car's superb refinement. The whole experience is improved further by our test car's optional Bang & Olufsen audio system. The digital set-up sounds great, and has speakers that rise out of the dash when it's switched on. The downside is that it is likely to add around £4,000 to the Q7's price tag.

Although the ride is firm, engine and road noise are almost absent. Making progress even smoother is a six-speed Tiptronic automatic gearbox, while quattro 4WD ensures there is no shortage of grip.

However, it's not the most fuel-efficient or eco-friendly diesel on the market. The Q7 struggles to better 25mpg and throws out 294g/km of CO2 from its exhaust pipes, meaning you'll pay dearly if you want to run it as a company car. And while on-road performance is first class, it's unlikely that Land Rover or Jeep will lose any sleep over its off-road abilities.

Even so, if owners do venture off the beaten track, the Q7 still offers a good degree of versatility, thanks to its capable four-wheel drive and adjustable air-suspension. More importantly, the torquey diesel easily has enough power to pull the car out of sticky situations.