Then last fall the board announced a search for a successor, saying it would look at candidates inside and outside the company.

FORBES: End of the Line

Circle said it would recruit a permanent successor to Mr Ali, with candidates from both inside and outside the company.

BBC: Hinchingbrooke: Ali Parsa steps down as chief executive

Outgoing President Nicolas Sarkozy shook hands with his successor in the palace's courtyard before leading him inside for a private meeting, at which France's nuclear launch codes were handed over.

BBC: Francois Hollande becomes France's new president

The long-time theologian is expected eventually to retire to a monastery on a hill inside Vatican City, with officials saying he will not be able intervene publicly in the papacy of his successor, though he may offer advice.

BBC: Pope Benedict XVI formally resigns to become 'pilgrim'