British motoring institutions don't come much smaller or more loved than the Mini, 35 years old this week. Right from the start the car's clever packaging (front-wheel drive, transversely positioned engine with the gearbox underneath) made it the world's most practical small four-seater. But it was also nimble, fun to drive and cheap, factors that have ensured its continuing appeal.

The shape has never dated, and hardly changed. Today there are thousands of second-hand models to choose from and the group two insurance level keeps the Mini reassuringly cheap to run. Fuel consumption is a paltry 40mpg, servicing costs are small, while parts are widely available at low prices.

In its purest form - the Mark 1, built between 1959 and 1967 - the Mini has become a classic, with its sliding side windows, deep door-pockets, 'magic wand' gear-lever and the tiny but adequate 850cc engine. You can pay anything from a few hundred to more than pounds 2,000 for this increasingly rare model.

The Mark 2 offers a 1000cc engine, and larger rear light clusters and windows: around pounds 1,000 will buy a very useable example. But it is the Mark 3, built since 1969, that is the most common and best known: prices range from a few hundred pounds for a tatty City model to pounds 4,000 for a good Mayfair. The only major change to the car has been comparatively recent: in 1992 it got a 1.2-litre, fuel- injected engine with a catalytic converter, to comply with emission regulations.

Of course, the Mini Cooper has the raciest appeal. The ultimate is the Mark 1 'S', which can cost pounds 5,000; other versions start at pounds 2,000. For the reincarnated Rover Cooper, expect to pay from pounds 4,000.

The big problem when buying Minis, especially old ones, is rust. The most common MOT failure points are rusty floors, rear subframes and sills. The body seams attract rot and the design traps dirt.

Mechanically, the engines are tough, probably too tough. Many owners think that servicing is a formality that can be overlooked. Listen out for clicking driveshafts on full steering lock and make sure the gearbox is quiet and engages easily. Buyers of Coopers need to be especially vigilant because they are so easy to fake up using a standard Mini.

Since there are so many second-hand Minis to choose from, you can afford to be fussy. But at Mini, Minis and Metros in Twickenham they were panicking because they had just one car: a 1986 City automatic. It had covered just 27,000 miles and there were plenty of bills and MOTs to confirm this. With four new tyres and a full service, at pounds 2,195 it was ready to roll. At the Catford Mini Centre, there were just a couple of sub- pounds 1,000 cheapies: a W-registered Mini 1000 as well as a tarted up, T-registered Clubman Estate, both for pounds 700.

At Gateside in Fife, a company called Mini Mart had an eclectic selection of Minis, from a pounds 500 1970 Cooper that needed a complete restoration through to a choice of two special-edition, K- registered 'Italian Jobs' at pounds 5,000.

As for Rover dealers, there was a time when they were embarrassed by the little car, but that has changed since the arrival of the trendy Cooper. At SMC in Slough, a 12,000-mile, 1992 Cooper in British racing green was on offer for pounds 5,995. Aside from a few stray paint chips, it was almost as new. But not quite as new as an L-registered Cooper with only 400 miles on the clock and costing just pounds 1,000 more.

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