The Abu Dhabi government sovereign wealth fund has bought equity units which covert into common shares equivalent to 4.9 per cent of the global bank’s outstanding shares. ADIA will have no say in the management of Citigroup, or be able to nominate a member to its board.

ADIA is notoriously secretive about its activities, but the announcement of the share purchase sheds some light on its investment portfolio. It is estimated to have about $850bn of funds under management.

It is not the only GCC investor in the bank. Saudi Arabia’s Prince Alwaleed bin Talal has a stake in the bank through Kingdom Holding Company.