Schroders, the UK fund manager, is set to return to the blue-chip FTSE 100 index despite a calculation error that deprived it of a merited place. However, a proposed merger between two housebuilding groups may mean its tenure is shortlived.

Schroders, with a market capitalisation of £3.6bn (€5.3bn), will be included in the index as of March 30, after a seven-month absence, thanks to the withdrawal of Anglo-Dutch steel group Corus, following its acquisition by India's Tata.