THE BMW X4 is a bit of a beast.

Oh it may sport classic coupe lines to soften the muscular stance of what the Germans call a Sport Activity Vehicle - but underneath the bonnet of the M Sport a monster lurks.

The top-of-the-range xDrive 35d model I drove isn't cheap at a shade under £50,000 - but for that you get 3.0-litres worth of diesel dynamite linked to super-slick eight-speed automatic transmission with manual gear-change paddles behind the steering wheel.

Helped by BMW's standard-fitted Launch Control, the six-cylinder powerhouse is a hoot propelling the X4 - smaller sibling of the X6 but nonetheless a big motor - to 62mph from a standing start in a shade over five seconds.

That's hot hatch acceleration from something that's the size of a tank by comparison. The brakes are refreshingly responsive though and there's a host of electronic aids to help keep you out of trouble but at heart this is a driver's car.

The all-wheel drive system is biased towards the rear wheels but can react in a heartbeat if it senses grip is being compromised elsewhere.

So the X4 is as much fun to take down a country lane as it is to cruise along a motorway - helped by a low centre of gravity, sharp steering, and terrific traction giving lots of confidence in corners.

BMW include a system called Driver Performance Control which can be set to Sport. This has the pleasing effect of speeding up the gearshift times and adding weight to the steering.

However, if you're feeling a little light in the wallet having paid for the X4 there is also an economy setting called EcoPro that - with the aid of an automatic stop/start system - reduces fuel consumption to a claimed 47.1mpg with emissions of 157g/km CO2.

If running costs are a key element then you will be better off with the 20d version which is best for fuel efficiency and low carbon dioxide emissions - but is not as much fun on the road.

Despite the 4x4 credentials, the M Sport is best kept on rather than off road as the low side skirts reduce ground clearance and the big road-friendly wheels make it prudent not to venture too far into the wilderness.

The X4 is more about coupe good looks and sloping rooflines than how much shopping you can get in the back. So while its boot - accessed via an automatically opening tailgate - can accommodate 500 litres of luggage, the more spacious and cheaper X3 can take an extra 50 litres. With the rear seats folded the X4's capacity is 1,200 litres - 200 less than the X3.

So if you want a practical BMW sport utility vehicle, the X3 is the clear winner - but if you want something to stand out from the crowd then the X4 gets the nod.

Initially I thought the steeply raked rear window would hinder visibility - but a rear reversing camera eased those concerns.

The cabin is a predictably classy affair with quality materials, figure-hugging sports seats and plenty of room for four adults. The excellent iDrive control system efficiently accesses the car's technical treats including the satellite navigation system standard on every model.