The Abu Dhabi Investment Authority, one of the world's biggest but most secretive state-controlled investment funds, made a small but significant step towards better disclosure by publishing its first annual review this week.

The report was light on details, and revealed little that was not already known by outside observers. However, Adia's report represents progress towards some transparency by the fund, and will be pored over by bankers hoping to manage some of its estimated $400bn-$450bn (€290bn- €328bn, ￡260bn-￡294bn) of assets.

Adia has never disclosed its overall size or issued reports, and until May 2008 its website was rudimentary, listing only its name, address and switchboard number. Senior management have granted only four proper interviews since it was set up in 1976 and, apart from employees, the only people usually allowed in its headquarters are senior global bankers and money managers seeking its business.