'You can carry enough diamonds on your naked body to set you up for life,' said Ian Fleming. Diamonds and gold - the most precious substances known to man - excite the imagination. But by geological accident, in the real world the two biggest producers of gold and diamonds are bitter political enemies - Communist Russia and white-ruled South Africa. Both countries vehemently deny that there are any contacts at all between them. But a top executive of South Africa's leading gold and diamond mining corporation was spotted recently at the Bolshoi Ballet in Moscow. What was he doing there? And was his visit part of an unthinkable secret partnership? Michael Cockerell investigates the secret world of gold and diamonds and the strange bedfellows it makes.