* 8 October: The Cabinet Office calls in the Metropolitan Police to investigate the Home Office leaks.
* 19 November: Junior Home Office official Christopher Galley is arrested and suspended from duty.
* 27 November: Shadow immigration minister Damian Green is arrested and held by the Metropolitan Police for nine hours on suspicion of "conspiring to commit misconduct in a public office, and aiding and abetting, counselling or procuring misconduct in a public office".
Mr Green's home and his offices in Kent and in the Houses of Parliament are searched. He is released on bail until a date in February.
* 28 November: Speaker Michael Martin is widely denounced for allowing police into the Palace of Westminster to search Mr Green's office.
Tory leader David Cameron criticises the "heavy-handed tactics" employed by Scotland Yard.
The senior civil servant at the Home Office, Permanent Secretary Sir David Normington, confirms that he called in the police following a number of leaks of sensitive information over "an extended period".
* 30 November: Home Secretary Jacqui Smith refuses to apologise for the arrest, saying the police had to be allowed to "follow the evidence where they need to" without interference from the Government.
But Commons Leader Harriet Harman says the processes allowing police to search MPs' offices in the House of Commons should be reviewed, adding that "big constitutional principles" are at stake.
* 1 December: Mr Galley insists he acted in the public interest. His lawyer Neil O'May says: "If there was ever a case of 'don't shoot the messenger', then this is it."
* 2 December: Scotland Yard announces an urgent review of its handling of the Whitehall leaks probe. British Transport Police chief Ian Johnston is set to deliver his interim findings to the Met's Acting Commissioner, Sir Paul Stephenson, within seven days, followed by a full report in two weeks.
* 3 December: In a dramatic statement to the Commons, the Speaker reveals the police had neither a search warrant nor his permission to raid Mr Green's Commons office.
Constitutional expert Geoffrey Robertson QC says it is "unlawful" for officers to enter the Palace of Westminster without the Speaker's permission.
But the Metropolitan Police insist they had authority in the form of written consent from Serjeant at Arms Jill Pay, who is in charge of Commons security.
Mr Martin pledges that police will never again be allowed access to an MP's office or parliamentary papers without a warrant and the personal approval of the Speaker. He announces his intention to appoint a committee of seven experienced MPs to look into the seizure of Mr Green's papers, computer and mobile phone.
* 4 December: In a Commons statement, Jacqui Smith defends the decision to call in the police, arguing that the "systematic" leaking of sensitive Home Office documents could threaten national security.
Assistant Met Commissioner Bob Quick, the senior officer in charge of the leaks investigation, says his officers made clear to the House authorities that they needed their consent as they did not have a search warrant. His comments appear to directly contradict Mr Martin.
Liberal Democrat leader Nick Clegg announces that his MPs will not sit on the Speaker's committee to look into the Green affair. The boycott is sparked by ministers' plans to ensure a Labour majority on the seven-member committee and to delay its deliberations until after the conclusion of the police operation.
* 7 December: The Sunday Times report that Mr Martin will stand for a third term. But a survey of 130 MPs by BBC Radio 4's The World This Weekend programme finds that 32 have lost confidence in him.
* 16 December: The Metropolitan Police announce they have received the final report into their probe into the Whitehall leaks.
The report, by British Transport Police Chief Constable Ian Johnston, said Mr Green's arrest and the search of his parliamentary office was lawful, but questions the "proportionality" of the manner of Mr Green's arrest.
* 18 December: The Commons home affairs committee announces that it will grill the Home Secretary, Mr Quick, the Home Office's top civil servant Sir David Normington and London Mayor Boris Johnson as part of its inquiry into the Green affair.
* 21 December: Mr Quick accuses the Conservatives of trying to undermine his Whitehall leaks inquiry after information is published that he claims endangered his family.
The Tories and their supporters are "mobilised" against the investigation "in a wholly corrupt way", he says.
He says he was forced to arrange for his children to be moved out of his home amid security fears after a newspaper published details about a business run by his wife.
He later retracts the "corruption" comment but remains under pressure to say sorry for the other comments.
* 22 December: Mr Quick offers an unreserved apology for all of his remarks shortly after Mr Cameron publicly demands a retraction of the "completely baseless allegation".
The deputy commissioner says: "I wish to make clear that it was not my intention to make any allegations and retract my comments. I apologise unreservedly for any offence or embarrassment that I have caused."
The Tories accept his apology and say they consider the matter closed.
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