It's difficult to imagine two less similar vehicles. On my right, the Porsche 911: uncompromising, hard to tame, unforgiving of mistakes. Beauty and brutishness in perfect harmony. And on my left, the Volkswagen Beetle. Tin can. Bug eyes. Star of Herbie Goes to Monte Carlo. Yet both of these classics come from the same stable, a dynasty that spans three generations of the Porsche family.

Ferdinand Porsche was born in 1875 in Bohemia. In 1898, he conceived a four-wheel drive electric car, which became 1900's prize-winning Lohner- Porsche Chaise. The technology was so far ahead of its time that 70 years later it was employed on Nasa's lunar buggy. His son, Ferry, was driving at the age of 10 and by 24 had created a mid-engined Grand Prix car for Auto-Union whose ground-breaking lightness contributed to race success between 1934 and 1937. In October 1936, a prototype of the VW Beetle, designed and built by the father-and-son team, rolled off the family production line and was quickly taken up by Hitler as a means of fulfilling his promise to build a people's car. In 1963, Ferdinand's grandson, Butzi, introduced the world to the 911. Some family...

An exhibition at the Design Museum, opening on 9 April, celebrates their remarkable contribution to 20th-century industrial design and, in particular, the 50th anniversary of the 911's forerunner, the world's first coupe, the Porsche 356. It is also a fitting tribute to Ferry, who died last Friday at the age of 88. The exhibition's curator, Gerard Ford, believes that the Porsche legacy deserves wide recognition. "The Beetle would be reason enough to stage an exhibition - it's the world's best-selling car and the template for all small cars thereafter," he says. "But the fact that VW also gave birth to one of the most expensive and glamorous of cars only adds to its significance. Porsche was the Freud, the Einstein of his field."

The exhibition features many of Porsche's most influential vehicles: the 356 which took the marque to victory for the first time at Le Mans in 1951; the 550 Spyder; and the 917, winner of seven out of eight world championships and recently voted the world's greatest racing car by Motor Sport magazine. The cars will be shown alongside scale models, drawings, photos and other original material.

But perhaps it's the Volkswagen, Porsche's utilitarian cousin, that should steal the limelight. It was never the best card to hold in Top Trumps ("0 to 60mph? As if"), or a sought-after addition to the Dinky Toy collection but it has charm and - dare I say it - accessibility on its side. And no Porsche ever had star-billing in a low-budget Seventies film series. (Even if many of them did go to Monte Carlo. And win.)

`Ferdinand Porsche: Design Dynasty 1900-1998', Design Museum, Shad Thames, SE1 (info: 0171-378 6055) 9 Apr to 31 Aug