UK's top civil servant Sir Gus O'Donnell steps down
Cabinet Secretary Sir Gus O'Donnell, the head of the civil service, is to leave his post at the end of the year.
He had previously been reported as saying he would step down before the next general election.
Sir Gus worked as John Major's spokesman in the mid-1990s. He later worked as permanent secretary at the Treasury during Gordon Brown's time as chancellor before moving to No 10.
No 10 permanent secretary Jeremy Heywood will become cabinet secretary.
Sir Gus's retirement on 31 December signals a major overhaul at the top of the civil service with his role being carved into three parts.
Mr Heywood will become cabinet secretary and the prime minister's principal policy adviser - but not head of the civil service.
That role will be taken over by a permanent secretary from within Whitehall after an interview process.
Mr Heywood will also not be the permanent secretary for the Cabinet Office, a role that will be taken on by former Football Association chief executive Ian Watmore, who is already working as the senior civil servant in the Cabinet Office.
'Outstanding civil servant'
The BBC's chief political correspondent Norman Smith said Sir Gus had been a "long-standing, highly-regarded" figure in Whitehall.
He described him as a "classic mandarin" who was a "permanent fixture at the highest echelons of government".
David Cameron said Sir Gus had been the "outstanding civil servant of his generation".
The prime minister's spokesman said Sir Gus felt it was "the right time" to stand down from a role he has held for six years.
He said Sir Gus had seen through the transition to coalition government and so it was "a good time" to hand over to his successor.
Asked why the role was being split, he said: "He is head of a department that has around 2,000 people.
"You are head of the civil service and all the permanent secretaries report to you, and you are secretary to the cabinet and principal advisor to the prime minister. It is a very big job."
Labour leader Ed Miliband said he had worked with Sir Gus at the Treasury and the Cabinet Office: "He was an outstanding public servant, unfailingly helpful, thoughtful and supportive in implementing the agenda of the government.
"He will be missed in government and I wish him well in the future."