WHEN is an SUV not an SUV? When it's a BMW.

If it's a BMW, then it's a Sports Activity Vehicle or SAV, and that's what the German manufacturer called the X5 when it was originally launched way back in 1999.

As a four-wheel drive with a chassis set up exclusively for performance on the road, BMW named it an SAV instead of an SUV, and the tradition has stuck.

The X5 is now in its fourth-generation and it's bigger and better than ever - and very much an SAV.

It is unarguably big - longer and wider than the Range Rover Sport and Porsche Cayenne though not quite as tall as the British rival. Its new, larger kidney grille gives it an extremely imposing look on the road.

However, its size means the luxurious, high-quality interior is cavernous yet more classy and comfortable than ever, with plenty of leg and headroom.

The new lay-out is more angular and contemporary, with the latest 12.3-inch infotainment display offering all the tech options a modern car buyer might think they want.

With a commanding view of the road ahead, the driving position is excellent, with comfortable but supportive electrically adjustable and heated sports seats. However, you'll be relying on the parking sensors or rear view cameras when reversing, as I found to my cost when faced with a recalcitrant white van driver on a narrow country lane. Never trust technology completely.

There's plenty of interior storage for families, with a large lidded box between the front seats, a good-size glovebox and spacious door pockets. The large boot can hold 645 litres of luggage - or a van-sized 1,860 litres with the rear bench down. The new X5 also comes with a two-section tailgate for ease of loading.

The latest clear and consistent BMW Live Cockpit Professional display and control system fitted as standard. Much improved, it comprises an instrument cluster and a Control Display - both 12.3-inch. The driver can use either the steering wheel buttons, iDrive Controller, touchscreen display, voice control or BMW gesture control, as they prefer.

Drivers can enjoy the full benefits of the car's intelligent connectivity capabilities by using its built-in SIM card and unlimited data allowance. Not only does this provide access to vehicle apps such as news, weather, office and online search, it also allows customers to use Intelligent Emergency Call - which automatically summons swift assistance in an emergency - and to receive regular updates for the navigation system's maps.

Of course, the X5 has always been praised for its road-focused performance, and that remains the case with the latest generation.

On the road, the six-cylinder xDrive30d benefits from Dynamic Damper Control, which electronically sharpens the car's dynamics at the same time as increasing ride and suspension comfort. The driver can select from two performance maps - for a more comfort-oriented or sportier driving style - using the Driving Experience Control switch.

It's incredibly quiet and relaxing to drive but offers plenty of punch for fast overtaking or more enthusiastic driving should it be needed. Maximum output of 261bhp is reached at 4,000rpm, while the 620Nm of peak torque can be summoned from 2,000-2,500rpm.

All variants feature the same sporty yet unnoticeably slick eight-speed automatic gearbox, and a 4x4 drivetrain that sends more torque to the rear wheels in order to emphasise its dynamism. I took the X5 up the A470 during a few days away in North Wales (and the now digital speed camera-covered ‘Evo triangle') and it was an absolute joy.

On the way back I had an equally enjoyable time on the A383 between Welshpool and Builth Wells. It may be big and heavy, but the X5 is a car you can have fun in.

Being so big, heavy and performance-orientated, efficiency is relative. Although it officially will return 47.1mpg, I managed a less impressive 31.9.

The M Sport spec suits the X5's thoroughbred genes. It brings 20-inch alloys, and sees wheel arch trim, bumper trim, rear underguard and side skirts painted in body colour. There's also extra-large air intakes at the front, an anthracite headliner, plus exclusive interior trim strips in ‘Aluminium Tetragon', which sounds like something from the future.

Standard equipment includes cruise control with braking function, Collision Warning and Pedestrian Warning with City Braking function, which now also alerts the driver when cyclists are detected.