HERE'S a car that combines pointless excess and surprising practicality better than almost anything else on the road.

But you can do something about the excess before you buy and the practicality is still there for the taking for the length of your ownership.

First, the excess. After choosing the diesel engined version of Bentley's ship-sized and high selling Bentayga SUV you'll be faced with an options' list as long as a well tailored arm.

One of the boxes you can tick adds £2,995 to the bottom line for a dash mounted Breitling clock with dark mother of pearl face and - not joking here - ringed with eight small diamonds. So it's both naff and impossible to read at the same time.

So, with nearly three grand back in your pocket, we proceed to the practicality part of the Bentayga equation.

Choose diesel as fuel and you save £26,900 over the cost of the full fat 12-cylinder petrol model, losing only modestly in the performance stakes. You may find that 168mph and zero to 62mph in 4.8 seconds is sufficient after all.

It certainly feels plenty fast enough, if not as bonkers quick as the petrol W12. Quite near the just announced V8 petrol Bentayga, though, and a miniscule £400 cheaper.

Your respect for the performance will then turn to astonishment when you glance the fuel consumption readout - over 500 miles the Bentayga diesel on test managed 31.6mpg, and touched 40mpg-plus on a gentle motorway run.

For such a huge and heavy car that's close to miraculous and made the 17.6mpg from the W12 driven some months earlier seem utterly dipso. It means an easy 500 miles per 18 gallon tankful and much less messing about at the pumps for the Bentley's time pressed owner.

And more time to enjoy driving a car that does a fine job of defying physics by making its 2.5 tonnes feel like a lighter vehicle when corners arrive - although never like a smaller one.

This is a very big machine, casting shadows over almost anything else in the car park and wide enough to make city driving an exercise in width judgement as the grocery deliveries van hurls towards you at must-make-the-slot speed.

In its element (wide, open road) the Bentayga is a near perfect way to transport four lucky people as far as they'd like to go, cocooned in leather lined luxury in a cockpit that makes you feel special every time the doors pull themselves closed the last few millimetres, thus saving you the bother of slamming them shut.

Despite its gargantuan bulk the Bentayga is merely very adequately spacious in the rear - not leg-stretchingly roomy - and the boot, while regularly shaped is modestly sized against something like... a Skoda Superb.