The Mittal family, which owns the world's largest steel group, has overtaken Belgium's wealthy Solvay family as the biggest shareholder in RAB Capital behind the UK-listed hedge fund manager's two co-founders.

The Mittals, through their investment vehicle Karrick, have taken up an option to buy a further 10 million new shares in RAB, taking their overall holding in the hedge fund manager to 53.4 million shares, or nearly a tenth of the group's share capital, according to a stock market announcement today.