The epic will mark the 90th anniversary of the first such rally, which was won by Prince Borghese of Italy.
This time around drivers include Christopher Dunkley from Lloyd's of London driving a 1935 Bentley 3.5 tourer, and John Stuttard, chairman of Coopers & Lybrand in China, in a 1934 Rolls-Royce.
Aristocratic polish is added by Lord Montagu, who is driving the oldest car in the rally, a 1914 Prince Henry Vauxhall. The royal contingent is led by Prince Idris Shah of Malaysia in a 1954 Studebaker Coupe.
The adventure has been organised by Phillip Young, who has helped put on previous Monte Carlo rallies, and his colleague, Peter Browning. Mr Young has negotiated rights of way across 22 countries, including China, Nepal, Pakistan, Iran and Turkey.
The rally starts in September next year and lasts 45 days. Drivers pay a pounds 25,000 entry fee and must carry all their own spares. No back-up vehicles are allowed, and as John Goldsmith, one of the drivers says, if you break down in the middle of nowhere "you're on your own, mate". But the organisers will use one sweeper car at the back to make sure any broken down cars can be helped to the next checkpoint on the journey.
Mr Goldsmith's firm, Goldsmith and Young, restores Aston Martins at its workshops in Wiltshire, and Mr Goldsmith himself is restoring a written- off Aston Martin DB6 "in order to win the race".
The steep entry fee has caused some problems. Sir David Steel, the former Liberal leader, is looking for sponsorship. The classic car rallying fanatic was originally going to China in his 1965 Rover, but he sold it, and will now probably go in his 1962 Riley.
Gerry Acher, head of audit at KPMG, is looking forward to the rally with a mixture of excitement and trepidation. He's driving his own 1932 Aston Martin International, and with an engine capacity of just 1.5 litres, one of the smallest cars in the rally.
"This little car has got to get us up to 17,000 feet [in Nepal], along with all our spares and camping equipment. The variations in conditions are going to be terrific."
Mr Acher's only previous experience of this type of thing was a four- day Euro Classic Car Rally, when his wife navigated. "She's very good at it. Both me and my co-driver, who's an expert mechanic, are useless at navigating, so it should be interesting."