IT'S EASY to assume that, once you reach a certain price level, you're only paying for the name.

A cheapo-budget watch will tell the time just as well - more or less - as a bespoke, hand-crafted Patek Phillipe that costs 10,000 times the price.

Except that the expensive watch was built by a watchmaker, with the finest materials available, is likely to be cherished for a lifetime and can do things that no plastic imitation will do.

And so it is with the £140,000 Bentley Continental Flying Spur Speed. The name should tell you that this is a car with a very definite purpose, and that is certainly the case: this is the world's fastest luxury saloon. The Flying Spur in regular form is something we're familiar with, a textbook example of understated elegance, a delicious selection of materials and attention to detail and a feel-good factor that can only be measured in smiles.

The Speed tag brings the Flying Spur a new degree of focus. You may notice the subtly dark-tinted chrome grilles and the fatter exhaust pipes, but it's the hardware changes that are the big news. As if 552bhp wasn't enough, the Speed gets the full 600bhp from its twin-turbocharged W12 (think two narrow V6 engines sitting side-by-side) and a truly epic 553lb.ft of torque. To fully exploit the extra performance, the Speed also gets revised and uprated suspension with a 10mm reduction in ride height and new specification springs, dampers, bushes and anti-roll bars. The power steering has also been recalibrated, with a bespoke wheel and tyre combination too. They've even loosened off the ESP, allowing more slip before intervention, should you decide to play a little on the way home.

You'd be forgiven for thinking then that Bentley has lots its collective marbles and turned the Flying Spur into some kind of giant hot hatch. Well, not on first acquaintance. Because you still pull gently on the chromed door handle and step into a cabin that can't fail to make you feel pampered and relaxed. Every surface is either high quality leather, chrome or wood, and even the odd plastic piece has more substance than you might expect. Electrically tweak the seat and steering wheel to get comfortable, and whatever cares you had have been safely left outside this automotive cocoon.

Fire it up, and there's a brief snarl and a faint quake as the huge amounts of torque make their presence felt, before it falls almost silent. Slip the automatic transmission into Drive and sail away, with no effort expended by you or the car. This is still a Bentley saloon: almost magically quiet, rolling along and dissipating bumps as if the road has been resurfaced just for you. Effortless doesn't do it justice.

But with the Flying Spur Speed, this level of comfort and luxury is only half the story. Even at a graceful pace, there are clear indications that the Speed is capable of so much more. The steering is surprisingly sharp and the huge amount of torque available from low revs makes short work of getting around. It's only a matter of time however before the road opens out and the Speed can really stretch its legs.

One lengthy squeeze of the throttle is all that's required for the Speed to prove worthy of its title as World's Fastest Saloon. The combination of a large capacity, multi-cylinder engine with turbocharging means there is massive power and torque whatever the revs. The automatic transmission slips between ratios almost imperceptibly, leaving you to stare wide-eyed as the needle on the speedometer rips around the dial at a spectacular rate. Acceleration is seemingly as rapid from 70mph as it is from 30mph, and the top speed of bang on 200mph never feels very far away. It remains faithful to the Bentley ethos though: you can hear a distance, cultured roar from the engine but it never intrudes.

Yet it can also play sports car when you reach a twisty road. The suspension changes have barely compromised the excellent ride, yet this undeniably large and heavy car feels nothing of the sort as you power through a bend. The long wheelbase makes it very stable, and the reassurance of four-wheel drive means it can be driven with real vigour. This is a truly entertaining car, but not one that requires the upmost attention at all times: once you leave the B-roads, slip it back into drive, switch on the cruise control and relax. No other luxury car is capable of such a double act.

FACTS AT A GLANCE

Bentley Continental Flying Spur Speed, £140,000

Engine: 6.0-litre petrol unit delivering 600bhp and 553lb.ft of torque

Transmission: Six-speed automatic transmission driving all four wheels

Performance: Top speed 200mph, 0-60mph in 4.5 seconds

Economy: 17mpg combined

Emissions: 396g/km C02