Laurence and Francois Graff
Rank 2017

The Letseng diamond mine in Lesotho is renowned for producing the world's most spectacular stones. Stepney-born Graff, 78, who is the largest shareholder in its owner, Gem Diamonds, divides his time between homes in the Swiss Alps, London, Cap Ferrat and New York and his 150ft yacht. He also owns the Delaire Graff Estate, a vineyard and winery with a hotel and restaurant in Stellenbosch – the Napa Valley of South Africa – and a contemporary art collection worth £430m. In 2013 he started collecting vintage cars. Graff Diamonds International, run by Graff's son François, 53, saw profits of £43m on £427m turnover in 2015.