MOTORING / Age cannot wither them: The Porsche 911 is 30 this year, the Mini is 34. What is the secret of their longevity? Roger Bell investigates

MOST cars have a design lifespan of under a decade, so the evergreen Porsche 911 - 30 this year - is in human terms over 200 years old. What is the secret of its longevity? Speed, agility and durability contribute to the legend but they do not fully explain it.

Perversely, the 911's appeal owes as much to a flawed concept as a race-winning performance. Although the flat-six engine is a paragon of smooth power, its unusual rear mounting (a legacy of Porsche's origins as a souped-up VW Beetle) gives sting-in-the-tail handling that brings out the best in a skilled driver. To drive a 911 well on testing roads is to be richly rewarded. Porschisti regard it as the ultimate motoring challenge.

But Porsche's oldest model is a mere baby compared with the 57-year-old Morgan 4/4, launched in 1936 to supplement Charles Morgan's three-wheelers. The running gear has been updated - today's incarnation has modern 1.6-litre (soon 1.8) Ford power - but the primitive chassis and suspension have changed little. Revolution at Morgan's is not pandering to convention, but dipping the body's ash frame in Cuprinol preservative rather than painting it. In a world of bland lookalikes, there is a place for an old-fashioned fun car that snubs fashion. The founder's son Peter and grandson Charles, still reject the advice of troubleshooter Sir John Harvey-Jones to modernise, arguing that the old way is the only way to preserve the time-warped anachronism that buyers seek.

Land Rover's Defender is a mere 45 and set to run and run. In 1948, when Rover launched its all-purpose off-roader (the Defender name is a recent acquisition), there was a need in post-war Britain for a tough, utilitarian farmer's friend. Inspired by the American Jeep, the LR was seen as a stop-gap, simple-to-make model which would keep Rover gainfully employed until better times. In identifying a market need, and meeting it brilliantly, Rover probably secured its future.

The genius of Colin Chapman, founder of Lotus, was in designing accomplished lightweights that humbled competitors through elan and agility. With his 1958 Lotus Seven he brought race-car handling and roadholding within the grasp of the impecunious enthusiast. It was to prove an irresistible formula. Today, Chapman's classic sportster, at 35 still the

epitome of the no-frills driving machine, lives on in the form of the Caterham Seven. The top Caterham, one of the fastest accelerating cars on the market, costs more than pounds 33,000, though there are much cheaper (and slower) variants, not to mention several imitators.

Rover's Mini, a year younger than the Lotus/Caterham Seven, also owes its enduring appeal to the genius of one man. Alec Issigonis eschewed convention. In turning the engine sideways, and fitting tiny wheels at the corners of a cubist body, he set new standards for space efficiency and handling. That the Mini was also classlessly chic, enormous fun and a giant-killer in motor sport were bonuses not in Issigonis's original script. Today, the Mini lives on as a nice little earner for Rover - the latest variant is an expensive convertible - and an entertaining antidote to characterless modern micros. The Japanese love them.

The Mini has been made without a break since 1959. Rover's evocative RV8 is the MGB (1962-1980), resurrected 13 years after MG's demise. A face-lift of questionable merit, and a Land Rover V8 engine under the bonnet, do little to disguise the origins of a born-again car that Rover sees more as a recreational pursuit trading on nostalgia than as everyday transport. Time will tell whether the limited-edition RV8 is a good investment.

Two sporting contemporaries of the MGB are still in production. The AC Cobra, currently the subject of a transatlantic dispute over design rights, lives on as a plaything for the rich. Although AC has changed hands, the cars made at Weybridge in Surrey have an unbroken lineage to the 1962 original. The quality and finish of AC's hand-built geriatrics, pounds 95,000 apiece without frills, is far better than it was in the Sixties, but the car's spirit has been dulled. The venom of American V8 power is tempered by weird gear ratios and power-

sapping emission-control equipment. Who wants a Cobra with cats?

At 31, the AC is a little older than the Marcos Mantara, which started life 28 years ago (with a surprisingly durable marine-ply chassis) as a Volvo-engined 1800. The bizarre styling of the Mantara - a golden oldie with trustworthy underpinnings - turns as many heads today as it did three decades ago. Modern running gear (which includes Land Rover's ubiquitous V8 engine) obviates the servicing and repair headaches associated with many small-scale specialist cars. It also gives it cracking performance and a wonderful exhaust waffle.

Alfa's long-lived Spider, 27 when production ceased earlier this year, was never so well endowed dynamically. Fiat's humdrum 124 - a boxy four-door saloon of conservative design - did not seem in 1966 to possess the qualities of a great survivor like VW's Beetle (still being mass-made in Mexico 55 years after its launch in pre-war Germany). Fiat ceased production of the 124 in 1974 but its progeny live on as the Lada Riva. The Lada factory at Togliatti on the Volga, named after a former chairman of the Italian Communist party, was the outcome of an Italo-Russian accord signed in 1966 to build a version of the 124 in the Soviet Union; since production started there, more than 11 million of the car known as the Riva since 1982 have been made. At pounds 3,905, the cheapest new car on sale in Britain, the outdated Riva 1.5E trades today on value for money and not much else.

The arrival this summer of a new Saab 900 that draws on General Motors technology (Saab recently joined Vauxhall, Opel and Lotus under GM Europe's corporate umbrella) will end the 23-year life of the car it supplants. The 900 was introduced in 1978 as Saab's first 'executive' car but its design stems from the 1970 99, the Triumph-engined model that took Saab into the mainstream from a quaint backwater. The secret of the 900's longevity is less easily defined than that of its Swedish compatriot, the Volvo 240, which has relied on tank- like solidity to reach its 19th birthday.

Dramatic looks and Ferrari-beating performance explain the enduring attraction for well-heeled enthusiasts of the Lotus Esprit, recently elevated to supercar status by the 170mph Sport 300. A timely face-lift in 1989 gave a new lease of life to the old Esprit - the only car Lotus makes, and that in tiny numbers, since the axe fell on the commercially unsuccessful Elan. But for how long? The future of troubled Lotus is still clouded by protracted talk of a management buy-out.

Jaguar's XJS, also 18 this year, is in better shape today than it was in mid-life crisis a decade ago, the victim of a one-model policy and poor quality. In addressing both problems, Jaguar put its dated dinosaur into intensive care and resuscitated it as a mature classic. So long as the most expensive 6.0-litre convertible (its V12 engine now 20 years old) undercuts Mercedes-Benz's cheapest SL, the XJS has a safe ticket to its 21st birthday.-

(Photographs omitted)