The new Bentley Mulsanne is not an adapted design of Bentleys from the past 80 years, but a clean sheet, bespoke piece of work.

So not only is its body and structure new, but so too is the 6.75-litre twin-turbo V8 under its bonnet. Yes, it uses the same outline architecture of the motor that first saw service in the 1959 Bentley S2, but the engine itself - the block, cylinder heads and internals - is completely new. Likewise the gearbox, which now has eight speeds.

What’s not new is the philosophy. The Mulsanne is still rear drive like the Arnage (and unlike the Continentals) and it still uses an open differential. It’s still aimed at people who like the idea of a traditional luxury carriage but still want to enjoy driving it. Bentley says that 80 per cent of Mulsanne owners will travel in the front.

So what’s it like? Broadly, very good indeed. You sit high in the car, surrounded by great slabs of wood and swaddled by the softest leather, and look down the long bonnet to those famed Bentley wings.

And while not everyone is going to agree with the way it looks, they’ll struggle to find just cause to complain about the way it goes. The headline figures - 505bhp and 104kgm of torque - improve only a little on the numbers boasted by the Arnage, but it is the fact that peak torque now arrives at 1750rpm instead of 3250rpm that dominates the way the car performs. It’s so effortless that you almost wonder if the Mulsanne even needs a gearbox, let alone one with eight choices of ratio.

It handles and rides like a Bentley too. The Mulsanne may look like a limo but it doesn’t drive like one. There is an underlying firmness to the suspension even in its softest setting that brings outstanding levels of body control at the inevitable cost of some compromise to bump isolation.

If you want to drive a car that copes with difficult roads with more grace and precision than any 2.6-tonne, four-seat saloon has a right to, look no further. The Mulsanne is not agile - nothing this heavy, sitting on that wheelbase, ever could be - but it is responsive, accurate and communicative. To call it fun would be no exaggeration.

And while one writing the cheque will most likely travel up front, the rear seats are just as tempting. In fact, if you’re to be denied the wheel, it’s probably a better place to pass the time than as a front seat passenger.

There’s all the room that you could wish for and more, plus a high seating position offering a fine vantage point from which to see not only what’s outside but also the whole cabin of the car, a pleasure denied those in the front. Also, those in the back sit closer to the car’s pitch and roll centre and are notably less affected by hard cornering, acceleration or braking.

Complaints are small but significant: there was notable wind noise at speed in the test car, and the way the state-of-the-art electronic interface and switchgear co-exist with the otherwise deeply traditional cabin has not been as successfully executed as you’ll find in a Roller. And, perhaps, old Arnage owners might find themselves mourning just a little that car’s coarser, noisier but more distinctive and characterful engine note. Maybe they’ll find the Mulsanne’s cabin design just a touch too clean; they might even consider the ease with which it can be driven actually relieves them of a part they quite enjoyed playing.

So Should you buy one? Yes. But don’t delay because it’s already sold out through 2010 and 2011. The first purpose-built Bentley in a lifetime has no serious flaws and some awesome talents.

It’s as effortless as a flagship Bentley should be, as luxuriously appointed and as capable and rewarding as any car flying the wings should be. It may be slightly less lovable than an Arnage, but much of that car's charm lay in its flaws. Those failings have been exorcised and what remains is a breathtakingly able, utterly admirable and endlessly enjoyable new Bentley.

Test conducted by Autocar UK