Motoring: The best luxury car I have driven this year: Roger Bell is smitten with the BMW 050i, part of the new 7-series

The new BMW 050i is not the quietest or smoothest car in its class of high achievers; Toyota's Lexus takes that accolade. It is not the biggest or most imposing, either; its arch-rivals, the Mercedes-Benz S-class juggernauts, outrank the 050i here. Nor is it the most luxurious; Jaguar can still teach the Germans a thing or two about hide-and-timber opulence. But any car connoisseur looking for the best sporting limousine for under pounds 50,000 would know, once he got behind the wheel of the 050i, that the search was over.

At pounds 43,950, the 050i is the more potent and expensive of a brace of new 7-series models powered by lightweight V8 engines that fill a perceived gap in customer needs between BMW's existing 'sixes' and 'twelves'.

The pounds 36,950 730i's 3.0-litre V8 (the smallest engine of its kind since the Triumph Stag in the Seventies) yields a generous 218 horsepower - fractionally less than the thirstier, pricier 735i 'six' it replaces. Just to confuse the issue, the old 730i - same name, smaller six-cylinder engine - is still listed by BMW as the base model, at pounds 27,500.

The performance of the 286hp 050i rivals that of the profligate V12 750i costing pounds 9,000 more, and BMW will need to upgrade its 5.0-litre flagship if this new sibling is not to steal its sales. Most rivals, never mind most upstart GTis, are decisively outgunned by the slingshot 050i, which is capable of a 50-70mph overtaking dash in 3.5 seconds. (The top speed is limited electronically to just under 150mph.)

The effortless brawn of its mighty engine impresses rather more than its tranquillity, however. Lexus drivers might envy the dashing BMW's dynamic prowess but will probably frown at the muted wail that goes with it. By normal yardsticks, the 050i is peace personified. By those of the Lexus, it is a little noisy.

Both the V8s come with a five-speed automatic gearbox so smooth in operation that shifts between ratios are seamless. Switch to 'sport' and the high-striding top gear, an overdrive intended primarily for motorway work, is omitted. When you need overtaking power, the engine and gearbox work together (they communicate by computer) to provide it.

There are smoother-riding luxury heavyweights than the 050i, which can succumb to the jitters on poor roads. Few of its peers, however, handle so well or inspire such affection. The agility of the 050i belies its size and mass; it is a worthy sports saloon. It steers precisely, without wooliness, and corners and brakes tenaciously, without deviation or slip. Never does it feel less than impeccably secure and composed. You have only to settle behind the wheel of a 050i to appreciate its class and quality. If the dashboard is not quite perfect - radio and trip computer are fiddly affairs - its layout is still one of the best.

ABS anti-lock brakes are included in the price, but you have to pay pounds 1,250 extra for ASC (automatic slip control) which prevents skid-inducing wheelspin in the wet. EDC (electronic damping control), which regulates the firmness of the suspension, noise-reducing double glazing, and a device that warns against parking bumps (the closer you get to contact, the more frenzied the bleeping) are further expensive options; so, too, are airbags, cruise control and an electrically closing boot-lid.

With these and other extras the 050i is likely to cost nearer pounds 50,000 than pounds 44,000. In standard trim, however, equipment in not especially remarkable for such an expensive car. You get the usual push-button playthings - powered seats, locks, mirrors, windows and sun-roof (totting up the number of on-board electric motors is a testing motorway game). Leather trim, walnut embellishment and remote-control security are included, too. Even without all the electronic systems that can make the 050i so extraordinary, you want for very little in the best luxury car I have driven this year.

Specifications

BMW 050i, pounds 43,950.

Engine: 3,982cc, 32-valve V8, 286bhp at 5,800rpm.

Transmission: five-speed automatic, rear-wheel drive. Top speed: 148mph, 0-60mph in 7.8 seconds. Fuel consumption: 16-24mpg unleaded.

Comparisons

audi V8, pounds 45,144 Refinements and more power have given Audi's flagship flop a new lease of life. Terrific performance.

Jaguar 4.0 Sovereign, pounds 38,300 Elegant, smooth-riding. Ageing six-cylinder engine lacks punch and refinement of new V8 rivals.

Lexus LS400, pounds 36,991 Toyota's first serious luxury car. The V8 engine and transmission are uncannily smooth and quiet; performance is strong; ride serene.

Mercedes-Benz 300SE, pounds 43,060 Cheapest of Mercedes' big S-class saloons makes do with six-cylinder engine; the refined V8, however, costs more than pounds 50,000.

(Photograph omitted)