The prospect of a white knight intervening in the €48bn ($60bn) bid by Sanofi for Aventis, began to fade on Wednesday following the appointment by Kuwait Petroleum Company (KPC), the biggest shareholder in Aventis, of UBS and Citigroup as financial advisers.

One banking source said: "This is a significant mandate for Citigroup and UBS to work on but it shows they did not think there was much chance of a rival bidder appearing."