Robert Tchenguiz, or Robbie as the Iranian-born property entrepreneur is known, appears to be at the eye of a financial storm. His stakes in Mitchells & Butlers and J Sainsbury have both fallen sharply in value and, with most of his investments held through contracts for difference, he faces regular punishing margin calls.

The imminent appointment of administrators to his Laurel Pub Company will reputedly cost him tens of millions, although it is small beer in the context of the estimated £850 million fortune he and his brother Vincent have built.

Some observers believe that if the financial crisis continues, it could send his empire into freefall. But such is the complexity of his web of businesses that nobody apart from his family and a small coterie of trusted business colleagues knows just how stretched his finances are.

Some cite last year's sale of his one third share in Whyte & Mackay, the Scotch whisky maker, netting him a profit of about £150 million in five years, as an example of his ability to make money in difficult businesses. At last week's Mipim, the property industry beano in Cannes, it was business as usual for Mr Tchenguiz, his yacht moored in its accustomed berth.

In his youth, the 47-year-old had a reputation as a playboy but these days he is more likely to be with his wife, Heather, and daughter Violet, with whom he lives in a mansion near the Albert Hall said to be worth £18 million.

Mr Tchenguiz, who enjoys boating, skiing, scuba diving and country sports, is trying to sell Somerfield, the supermarket chain. The deadline for second-round bids was last week and Asda, Waitrose and the Co-op are favourites. As with most of his deals, it would take a team of forensic accountants to work out just how much he makes but it is unlikely to be enough to stop him being buffeted by today's financial crosswinds.