For £165 a month you can take out a loan that will make a two-litre Ford Sierra or Mazda 626 yours in ten years' time. The car won't be worth much then, and you'll have spent nearly half of your £20,000 outlay on interest charges.

Or, you could follow David Wickers' example and channel the money into the restoration of a vintage Bentley. Then you'll end up with a car at the upper end of the classic market that looks like new, is glorious fun to drive, and would fetch more than £100,000 if you decided to sell it.

There is, of course, a catch in this financial illustration. To benefit from it, you need to have bought your Bentley cheaply, years before the classic boom started.

David Wickers got his 1926 three-litre Speed Model open tourer in 1960 for just £200. In those days, however, that was still a hefty sum for a 24-year-old to find. He sold a vintage 20-horsepower Rolls-Royce to raise the deposit and paid off the balance by hire-purchase installments. Then, after driving the car for some years, David realized that the Bentley needed major attention if he was to continue to enjoy the old warrior's immense torque and 90 mph top speed.

Thus began a restoration that was to absorb ten years and an awful lot of money and patience. But David now has the car back on the road and is delighted that his determination to see the project to completion never wavered.

"Driving it again is like stepping back in time - it feels just like the same car," he says.

A finance broker in Exeter, Devon, David is obviously well aware of the fact that the Bentley represents a blue-chip investment. But he hasn't devoted a decade of spare time to the car for that reason. How could he have forecast today's price levels when he bought the Bentley 29 years ago, or even when he began the restoration in the late seventies?

"I've never bought a car for its investment potential," he insists. "I just love driving old cars and the challenge of maintaining and running them."

He hasn't even worked out the total bill for the Bentley's restoration. "I've never added everything up. It feels like £20,000, but it could be less," he says. "Even if the facilities had been available for the car to be restored in two years, I couldn't have afforded the expenditure. I just took it steadily and plodded on, and in that way I kept the bills reasonably under control."

What his experience proves is that even expensive cars can be tackled by enthusiasts with only basic mechanical ability, who have to farm out all the major jobs. "You don't have to be very skilled at restoring cars to be better than me," he admits. You do, however, need unfaltering persistence and a willingness to handle mundane chores like stripping and cleaning. A nose for local, inexpensive sources for some of the work also helps.

Once he had decided on a full restoration, David settled on a widely accepted policy: inspect every component, assess its condition, and replace it if it is beyond salvation. He also wanted to return the car to its original appearance, although finding out exactly how it looked when it was first registered on 26 June 1926 proved impossible. Numerous original parts, including the windscreen and the wings, had already disappeared by the time he acquired the car in 1960, when it was painted in several shades of green.

David actually met the Bentley's original owner, one Mervyn Rollason, in the late sixties. Mr. Rollason, from Warwickshire, said it had been his first car and a twenty-first birthday present. But he had crashed it in Italy during his first year of ownership, and the vehicle had had to be shipped back to England for repair. Meanwhile, Mr. Rollason bought himself a 4½-litre Bentley; he was on his seventh Bentley, the only make of car he had ever owned, when David talked with him.

At that time, however, there were no plans to restore the three-litre car, so David didn't ask about its original appearance. When he did start the project, he had lost contact with the former owner; but in any case the car's registration document revealed that it had been painted blue. Only when the restoration was well under way did confusion arise: David bought a book on the history of Vanden Plas, the coachbuilders, which revealed that the car had been finished in blue and grey. But which parts were painted in which colour remained a mystery.

One of the first jobs was to repair the car's wooden frame, much of which had been attacked by woodworm and rats. Here a local craftsman came in handy: David found a young joiner who had never worked with cars, but was able to replace sections of the frame that had degenerated beyond rescue. The original wood still makes up more than 60 percent of the frame, but the discarded sections were used as patterns for new pieces.

David decided on a simple polished finish for much of the aluminum bodywork, but this plan had to be abandoned after stripping of the old paint exposed an assortment of filler and scratches. He eventually compromised with a light, non-metallic silver paint on the bonnet to make it look as much as possible like polished alloy, but admits that the similarity is not as close as he would like.

The body paneling from the scuttle to the rear of the car had oxidized and needed replacing. Here David was lucky in finding a retired panel beater who relished the chance to get involved with such a rare challenge as a vintage Bentley. He provided excellent, inexpensive craftsmanship, and also advised against David's idea of having fabric-covered bodywork, a popular choice in the pre-war period. In the event of an accident, the fabric would have to be stripped from the underlying metal before repairs could be made.

The panel beater also made the windscreen and the wings. The windscreen style is based on a photograph of a 1925 works Le Mans Bentley, while Le Mans cars also provided inspiration for the blade-type front and rear wings. David knows that his car - chassis number RT 1550, engine number RT 1530, body number 1278 - was originally fitted by Vanden Plas with prominent valences on the inside of the wings. But he felt the valences were too bulky and preferred the racier look of the simple blade wings. These have been made in steel to withstand the pounding they take on the road.

As an illustration of the problems that can arise during a wheels-up restoration, the panel beater had to sketch out on the floor of his workshop the Bentley's tyre size to obtain the proper wing radius and then make an allowance for the wheel's bounce height. But the springs that were ordered for the car have given a ride height that is too great by about two inches. Fortunately, this flaw isn't really noticeable unless it's pointed out to an observer; and anyway, David is hoping that the springs will eventually settle down to give the correct relationship between the various components.

A crash at some stage in the car's past - possibly the one in Italy - had left damage to the chassis and front axle. A bend in the chassis near the steering box mounting had been strengthened with a welded-on plate, but an engineering company in Sussex removed this and straightened the original pressed-steel members. The front axle was straightened, and new kingpins and bushes fitted by the Rolls-Royce/Bentley specialists, Hoffman of Henley-on-Thames, Oxfordshire.

The engine is an impressive, three-foot high construction with the extraordinarily long-stroke dimensions that were fashionable when W. O. Bentley designed his famous three-litre unit in 1919. The bore and stroke are 80mm x 149 mm (conrod length is more than 11½ inches!), and peak revs occur at only 3300 rpm. But there is an overhead camshaft driven by bevel gears and a vertical shaft, four valves per cylinder, and twin-spark ignition provided by two ML magnetos. David's car has a compression ratio of 5.6:1 - it was as low as 4.3:1 in some earlier Bentleys - and twin SU carburettors. Output is rated at 85 bhp.

The five-bearing, forged-steel crankshaft was reground and the bearings remetalled. New parts were obtained including piston rings, rockers, valves, valve springs and guides; but replacement pistons were not available at that time, and David reluctantly kept the originals. The engine components were then given to Martin Morris, a vintage car enthusiast in Devon, best known for his racing performances in ERAs, for reassembly.

Martin decided that as a safety measure the renovated crank should be crack-tested, and was told that it had failed. This meant that David had to buy another crank and have that reground, a process that must have tested his dedication to the project.

"You have to be pretty stoic about the expense when you have to pay to get the same job done twice during a restoration," he says. "I should have had the original crack-tested in the first place, but you don't always think of these things."

Some Bentley owners lighten their cars' flywheels, but David has left his standard. He also retained the original cone clutch, simply relining it with Ferodo material, rather than modifying the car by installing a modern multi-plate clutch. Fortunately, the components in the four-speed gearbox required no attention.

Many parts required during the restoration were supplied by D. H. Day in Wroughton, Wilts, the type of firm without which the classic movement would founder. From his 25-page catalogue, proprietor Donald Day offers a vast array of chassis and engine components for the "W. O." Bentleys made prior to the company's takeover by Rolls-Royce in 1931. You can spend as little as 16p on an SU carburettor float chamber plug washer, or £2850 on a nitrided-steel crankshaft for an eight-litre, six-cylinder engine.

For David Wickers' car he provided a stream of parts including a crown wheel and pinion, lynch pins, tie rods, spring gaiters and bushes, a brass cover for the starter motor and alloy support brackets for the body.

David particularly remembers Day's response to his telephone plea for the alloy brackets. "I made those 11 years ago, and you're my first customer!" Day responded.

Final assembly of the car was undertaken by Fred Gudgeon, in Ringwood, Hants, an acquaintance David had made through their common interest in Morgan cars and three-wheelers. Gudgeon rebuilt the Andre friction shock absorbers and the rear axle, set up the steering mechanism correctly, and made running boards and wing irons to accept the new wings.

Mating the body to the chassis was tricky because there were areas where the body did not quite fit by perhaps a quarter or half an inch. Gudgeon's solution was to prepare some thin splines of ash wood of the correct shape, Araldite them to the body, and then bolt the body to the chassis. When the components were separated a week later, the Araldite had acted as a filler and made good the inaccuracies between the body, the spline and the chassis.

There is a network of car craftsmen in the Hampshire-Dorset area that can handle a variety of jobs, so while the Bentley was with Fred Gudgeon he sent out parts for nickel-plating and the upholstery for attention. The upholsterer, Ken Day of Wimborne, handled the seats (in Connolly leather), the interior trim, the hood and its bag, and the tonneau cover, while new Wilton carpets now line the car's floor. Fettling the Bentley, incidentally, proved a turning point in Fred Gudgeon's life. The job persuaded him to use his background in the engineering industry to become a fulltime restorer. Now his workshop is full of historic vehicles from Bullnose Morrises to Aston Martins and motorcycles.

Ironically, after the leisurely pace of the actual restoration, the car's bedding-in process became a frantic hurry when David decided to drive it to a Bentley Club function in Brittany only two weeks after collecting it from Hampshire. "A universal joint broke up, the autovac was playing up, there was a noisy tappet and the brakes needed adjusting," he remembers.

But the problems were solved in time -a UJ from a Jaguar V12 was fitted into the Bentley housing, and thus is undetectable from original - and a successful trip to France was made with three passengers. David has now completed 2000 miles in a car that is surprisingly practical in modern traffic, even though it has a central throttle pedal.

"I've seen an Alvis with a central throttle turn over when the driver hit the wrong pedal in a panic stop, but it doesn't bother me at all," he says.

Of the 3051 Bentleys made, 1636 were three-litre models. The Bentley club believes that less than 700 survive. Three-litre cars were used by the 'Bentley Boys,' the factory's colourful team of drivers, to win two of the five Le Mans victories the marque recorded from 1924-30. The Speed Model was distinguished by its twin SU sloper carburettors, sporting camshaft, and 9-foot, 9-inch chassis; a longer or shorter chassis could be ordered. David's car is also known as a Red Label model, due to the backing colour beneath the Bentley emblem on the radiator shell.

It cruises at 60-65 mph and lugs high gears magnificently up Devon's innumerable hills. The 400mm drum brakes stop the 3200-lb car reasonably well, but high pedal pressure is needed. Bentley had started fitting four-wheel brakes only two years before this Speed Model was made.

Sitting behind that immense bonnet, you watch the road reeling in over the winged-B radiator mascot and feel a gentle thrumming from the big four-cylinder engine. An exhaust system made by Donald Day provides a civilized note, but from the smiles and waves the Bentley arouses by its progress, you feel that the public wouldn't be offended even if it did rattle their window panes. The ride is fairly harsh, but David is still experimenting with damper settings, and reckons the whole car will continue to improve until 5000 miles of running-in have been completed.

Meanwhile, this gorgeous reminder of aristocratic motoring in the twenties returns 20-25 mpg, and under a Bentley Drivers Club limited-mileage, agreed-value scheme costs only £250 a year to insure. Many Ford and Mazda drivers probably pay more.