Sir Bernard Hogan-Howe is to retire after five years as the Commissioner of the Metropolitan Police .
He will stay until February to allow the Home Secretary and the Mayor of London to appoint a successor.
Only last week the Deputy Mayor for Policing and Crime Sophie Linden was quizzed by the London Assembly about relations between the Mayor’s Office and Britain’s most senior policeman.
She said relations were excellent and he can “plan his Christmas card list” although relations between the two were cordial rather than warm during the meeting.
There is no clear indication that his departure is directly linked with the arrival of Mayor of London Sadiq Khan, although Scotland Yard's top job is increasingly becoming a political appointment by default. His contract was due to end in September so he is leaving seven months early.
Mayor Khan had indicated he wanted to pick his own man and question Sir Bernard's judgment. Only last week the Commissioner admitted he should have been more aware of public concern over the use of spit hoods, earning a rebuke from the Mayor.
In a statement, the Mayor thanked Sir Bernard and said he had "enjoyed working closely with him over the last five months".
Sir Bernard was appointed to the role in 2011, and was quickly plunged into the response to the London riots. He ensured the 2012 London Olympics passed off without incident and oversaw and 18% drop in crime during his tenure.
Increasingly, he was occupied with the threat of global terrorism as conflicts in Syria and Iraq brought threats to major western cities and saw Londoners leave to join the fighting.
The murder of soldier Lee Rigby in 2013 in Woolwich made that threat a reality. His attackers were stopped by firearms officers from the Met and later convicted and sentenced to life in prison. The number of firearms officers has increased overall in an attempt to deter attacks and reassure Londoners.
The MPS has already saved more than £600million and sold its historic headquarters at New Scotland Yard for £370million. It will move its HQ and the famous spinning sign to a refurbished police building in a few months.
Sir Bernard said: “I am so proud of the remarkable men and women who serve Londoners as police officers and staff and make this such a safe place for people to live, work or visit.
“I want to thank all of them for what they do, and the risks they take each day to protect the public.
“I want to thank all the partners we work with in government, in City Hall and across London. And I want to thank the public for the support they show the Met, and have shown me personally, as we do our difficult jobs.
“I came into this job determined to fight crime and make the MPS the best, most professional police service. I wish my successor well as they take on this amazing responsibility.
“It has been a great privilege to be the Met’s Commissioner. I have loved my time in the role and I have loved being a police officer.
“It’s the most rewarding of jobs to protect good people and lock up the bad guys.”
Home Secretary Amber Rudd also paid trip to the Commissioner's efforts in the face of increased international terrorism as well as his work keeping the Olympics incident-free.