But there is nothing genteel about its performance. Despite weighing well over two tons and having the aerodynamic efficiency of a medieval fort, this awesomely expensive car accelerates like a rocket. Nothing this side of Fantasy Island equals its seductive blend of muscle and dignified luxury.
Change the radiator grille and the Turbo RL could be a Rolls- Royce Silver Spur. But the turbocharger gives the Bentley a great deal more power. Rolls-Royce has always been coy about what its engines produce, and generations of journalists have meekly accepted - and quoted - the company's description of the Rolls's power as sufficient. In fact, the naturally aspirated 6.7-litre V8 engine produces 241bhp at 3,900rpm. Thanks to its turbocharger, the Bentley cranks out 352bhp at 4,200rpm.
A car's response to the accelerator depends to a great extent on how much torque its engine develops. Such words as 'prodigious' and 'massive' are often used to describe the Rolls/Bentley motor's torque. Today's version of the supercharged vintage Bentley delivers 553lb ft - the highest figure for any production car. It exceeds the non-turbocharged engine's maximum by 49 per cent. The result is a car whose turbine-smooth mid- range acceleration has to be experienced to be believed. When you overtake, you get the impression that an obliging wizard has turned an articulated lorry into a building. Added impetus is provided by switching the automatic transmission to the 'sport' mode.
The original Bentley Turbo worked wonders for the marque's image, but had more power than poise. Today, the computer-controlled suspension system reacts to various critical inputs in a fraction of a second, automatically switching from soft to firm when crisp handling becomes more important than the ride (which is extremely smooth by most standards, but not quite good enough to merit five-star rating). The electronics combine with giant Avon Turbospeed tyres to make this rather long car remarkably agile.
Passengers express amazement as it makes swift, sure progress along challenging, winding roads and circles roundabouts as confidently as an Intercity 125 express on its rails. The standard Turbo R is 4in shorter but otherwise indistinguishable (Rolls-Royce Motor Cars Ltd has not even bothered to take a photograph of the RL for its files, so you will have to imagine the extra inches). It is significantly lighter, more nimble, and costs a bit less.
Anyone wealthy enough to run such a car will not be worried by huge fuel bills, but it is irritating to stop so often on a long journey. The time spent filling the tank - I pumped almost 90 gallons in four days - recalls the story of the tortoise and the hare. That said, an average of 14mpg revealed the Turbo RL to be as economical as the much slower Rolls-Royce Silver Spirit in which I drove 3,500 miles in 1991.
Smooth, sophisticated, supercar performance is what makes the Turbo RL far more appealing than any Rolls-Royce, despite the latter's unrivalled image of wealth and status. But flawless quality cannot be taken for granted. I have experienced a number of problems and niggles while driving Rolls-Royces and Bentleys. The Turbo RL's included the fuel filler cap (it kept opening), a squeak in the steering, and a button that came off a switch.
Faults that would be irritating in a Reliant Robin are unforgivable in a car priced at pounds 140,612. And that, incidentally, is almost pounds 40,000 more than Rolls-Royce paid for Bentley Motors Ltd in 1931.
Bentley Turbo RL, pounds 140,612
Eight-cylinder turbocharged, intercooled engine, 6,750cc, 352bhp at 4,200rpm. Automatic transmission;
0-60mph in 6.7 seconds, top speed 147mph. Average fuel consumption 14mpg.
Rolls-Royce Silver Spur, pounds 119,428
Shares the Turbo RL's long-wheelbase body, but not its turbocharged engine. Less performance, more prestige.
Mercedes-Benz S600, pounds 92,100
Not the most popular and beautiful of status symbols, despite this year's facelift, but superbly engineered. Has double-glazed windows and self-closing doors.
Ferrari 456GT, pounds 145,999
Ferrari's sleek and surprisingly practical new flagship commends itself to those for whom pace is more important than space.
Double Six, pounds 56,200
De luxe version of Jaguar's XJ12 is a fast, luxurious car with a refined 6.0-litre engine, superb handling and a wonderfully smooth ride.