Rallying: All for a night at the opera: 1968 revisited as the London-Sydney Marathon revs up: Derick Allsop reports on a demanding race revived today in vintage form

AT Chelsea Harbour this morning, 212 drivers and navigators will look out and visualise the Sydney Opera House. On the more immediate horizon are thirty days and 11,500 miles of motoring.

These participants in the Lombard London-Sydney Marathon are re-enacting the famous 1968 trek, complete with period cars. The winner of the original event, the Scotsman, Andrew Cowan, leads the field in the same Hillman Hunter.

Ahead of these doughty veterans - some are of considerably greater vintage than their cars - lie 41 special stages, across Europe, in the mountains of eastern Turkey, along the plains of India and down through the Australian outback.

In an age of hi-tech and highly competitive motor sport, the historic car movement represents an alternative outlet and philosophy for the enthusiast. It is significant that, after breaking a lengthy association with the RAC Rally, Lombard should have chosen to link up with this adventure.

Those involved, however, maintain this is still a serious sporting contest, not merely an extravagant geriatics' outing. Nick Brittan, the event director, said: 'Don't get the idea this is a leisurely commemorative run. It's a no-nonsense, highly competitive race. The 1968 event was more about stamina. This time the accent is on speed and skill.'

The mobile headquarters will be run by a 20-strong staff equipped with the latest satellite technology. The clerk of the course, Les Needham, said: 'It's like organising six RAC rallies with the added difficulty of 18 frontiers, six languages and eight different currencies. In '68 the only way they got the results out of Afghanistan was by morse code from the British embassy to Whitehall.'

Cowan's Hillman has been loaned by the Royal Scottish Automobile Club and rebuilt for pounds 40,000. 'It wasn't the quickest car in '68,' he said, 'but it was tough and rugged and it did the job. It could do it again. This is the longest event since the original one and in many ways it's going to be even tougher and more competitive.'

The man who almost won in 1968 is the marginal favourite. Roger Clark, the last Briton to win the RAC Rally, was leading within a day of the finish when a broken axle put him out of contention. He borrowed a replacement from a local fisherman and came in 10th. Now 53, he drives a Ford Escort which he and his 22-year- old son, Matthew, have built by hand. 'It's lightweight, it's tough and it's quick, the three ingredients needed,' Clark Snr said. 'Twenty-five years ago I thought I had my name on that trophy, and it was one I really wanted to win. It's time to have another go.'

The most luxurious car in the Marathon is a Rolls-Royce Corniche convertible, owned by an Australian, Tony Wilson. The oldest, a 1953 Morgan, is driven by the oldest female competitor, 66-year-old Pam Durham, born in Sydney but now living in Portsmouth. 'I'm a tough old bird,' she said. 'I had too many kids around my ankles when the original event ran.'

To the undisguised relief of some officials, one entrant not off on the adventure is Mark Thatcher. He has withdrawn because of the problems Pam Durham had 25 years ago. It is his turn to discover the trials and tribulations of parenthood.