'Plebgate' row: Timeline
Allegations that Conservative chief whip Andrew Mitchell called some police officers plebs during a row in Downing Street cost him his government job.
But the scandal has since embroiled the police in accusations that they have not been sufficiently robust in disciplining officers accused of trying to discredit the MP as part of a campaign to "toxify" his party.
BBC News looks back at how the row unfolded.
19 September 2012
Conservative MP Andrew Mitchell, then the government's chief whip, has a row with police officers who would not let him cycle through Downing Street's main gate.
20 September 2012
The story is revealed in the Sun newspaper, which reports that he swore at the officers and called them "plebs" who should learn their place.
21 September 2012
Mr Mitchell denies using the word "plebs" but apologises for being disrespectful.
24 September 2012
Mr Mitchell says he wants to "draw a line" under the incident, telling reporters: "I did not use the words that have been attributed to me."
But speculation about the exact words he did use continues. Deputy Prime Minister Nick Clegg urges him to explain "fully and in detail his version of events".
25 September 2012
A police log of the incident, appearing to confirm previous reports and contradict Mr Mitchell's position, is leaked to the Daily Telegraph.
7 October 2012
Mr Mitchell remains in his job, but members of the Police Federation wear "PC Pleb" T-shirts at demonstrations against police funding cuts at the Conservative Party conference.
12 October 2012
Three local representatives of the Police Federation meet Mr Mitchell at his Sutton Coldfield constituency office for 45 minutes, telling reporters afterwards that he had still not disclosed the precise words he used in the incident.
They criticise him for implying that the Downing Street officers' accounts are not accurate. The chief whip has "no option but to resign", one representative concludes.
17 October 2012
David Cameron tells Parliament that what Mr Mitchell "did and said" was wrong, but since he had apologised and the officer involved had accepted his apology, he should be allowed to get on with his job.
But opposition leader Ed Miliband says that, despite the apology, Mr Mitchell is "toast".
19 October 2012
Mr Mitchell resigns, claiming the "damaging publicity" means he can no longer do his job.
In his resignation letter to the PM, he writes: "The offending comment and the reason for my apology to the police was my parting remark 'I thought you guys were supposed to f***ing help us.'
"It was obviously wrong of me to use such bad language and I am very sorry about it and grateful to the police officer for accepting my apology."
16 December 2012
A police constable with the diplomatic protection group is arrested on suspicion of misconduct in a public office, and suspended from his duties in connection with accounts of the Downing Street incident.
18 December 2012
CCTV footage, broadcast on Channel 4 news, casts doubt on the police officers' version of events.
The police log said Mr Mitchell's use of a number of expletives had left members of the public looking on "visibly shocked". But the footage suggests that no-one other than the officers involved were within earshot.
Mr Mitchell says he has fallen victim to a "stitch-up".
19 December 2012
Scotland Yard says it is opening an investigation into claims that an officer gave false evidence.
Metropolitan Police Commissioner Bernard Hogan-Howe says: "The allegations in relation to this case are extremely serious. For the avoidance of doubt, I am determined there will be a ruthless search for the truth - no matter where the truth takes us."
In the ensuing months, eight people are arrested and bailed under the investigation, codenamed Operation Alice, including five police officers.
7 March 2013
Mr Mitchell launches libel action against the Sun over its reporting of the "plebgate" incident.
19 September 2013
A year after the original incident, former home secretary Jack Straw criticises the "inordinate and unjustified" length of time the investigation has taken.
15 October 2013
Independent Police Complaints Commission deputy chair Deborah Glass says the IPCC disagrees with police chiefs' decision not to hold misconduct hearings on the three Federation officers involved in the October 2012 meeting with Mr Mitchell.
The IPCC releases a transcript of the meeting - from a recording made by Mr Mitchell - which shows that, while he admitted swearing, Mr Mitchell denied using the word "pleb" or insulting the police.
However, after the meeting the three officers said he had refused to elaborate on what had happened and should resign.
Home Secretary Theresa May says it would be "quite wrong" to take no action against those officers. The chief constables of their forces say they will welcome the opportunity to appear before the Commons Home Affairs Select Committee to explain why no action was taken against them.
16 October 2013
David Cameron says Mr Mitchell is "owed an apology" by police over the row.
It also emerges that an internal report which ultimately found no misconduct case to answer by the three officers who met Mr Mitchell at his constituency office had initially proposed disciplinary action.
21 October 2013
The three officers, Ken MacKaill, Stuart Hinton and Chris Jones, apologise for their "poor judgement" in talking to the media following their meeting with Mr Mitchell. They say they did not "plan or intend to mislead anyone about what occurred".
But friends of Mr Mitchell tell the BBC the statement is "a regrettable non-apology".
23 October 2013
The three Federation officers insist to the Home Affairs Select Committee that they do not owe Mr Mitchell an apology. They say they stand by their "accurate" account of the meeting and Mr Jones says he is "not convinced we have done anything wrong".
But the head of West Mercia Police tells the committee the handling of the affair was "clumsy" and the internal report and its recommendations should be independently reviewed.
27 October 2013
Sir Hugh Orde, head of the Association of Chief Police Officers, says the conduct of the three officers fell "below that required" and they should apologise.
31 October 2013
Three civilians and five police officers on bail over the plebgate affair are re-bailed to a date in late November.
3 November 2013
The IPCC says it is conducting its own investigation into the conduct of the three Federation officers - Ken MacKaill, Stuart Hinton, and Chris Jones - saying there were "procedural irregularities" in the earlier internal police probe.
It also emerges that the trio will be called back before the Home Affairs Select Committee. Its chairman, Labour's Keith Vaz, says MPs were "appalled" by the officers' original evidence and that if they did not "correct the record" they would be in contempt of Parliament.
6 November 2013
Stuart Hinton apologises to the the home affairs committee for an "inadvertent error" in his earlier evidence. He also says he regrets the "distress" felt by Mr Mitchell and his family during the whole saga. Chris Jones, also appearing before the committee, insists he did not mislead MPs over his disciplinary record.
26 November 2013
PC Keith Wallis is charged with misconduct in a public office, accused of falsely claiming to have witnessed the incident in an email to his MP. But prosecutors say there is insufficient evidence to show an officer in Downing Street lied in his account of what happened.
Separately, the Independent Police Complaints Commission says five members of the Metropolitan Police's Diplomatic Protection Group will face gross misconduct proceedings linked to the subsequent row, meaning they could lose their jobs. The BBC understands that the officer at the Downing Street gates on the night of the incident is not one of the five.
4 December 2013
PC Toby Rowland, the police officer who was on duty at Downing Street, says he is going to sue Mr Mitchell for libel over comments he made to the media following the incident.
16 December 2013
PC Keith Wallis appears at Westminster Magistrates' Court charged with misconduct in a public office, accused of falsely claiming to have witnessed the incident. He did not enter a plea.
10 January 2014
PC Keith Wallis admits misconduct.
5 February 2014
Metropolitan Police chief Sir Bernard Hogan-Howe meets Mr Mitchell to apologise for PC Keith Wallis's role in the affair.
6 February 2014
PC Keith Wallis is sentenced to 12 months in prison. Passing sentence, Mr Justice Sweeney said Wallis had been guilty of "sustained, and in significant measure, devious misconduct which fell far below the standards expected of a police officer".
26 February 2014
PCs Keith Wallis and James Glanville are sacked for gross misconduct. The Met said Mr Glanville was dismissed for passing information about the incident to the Sun newspaper.
27 April 2014
It emerges that PC Toby Rowland is seeking up to £200,000 in damages from Mr Mitchell for suggesting he was not telling the truth about the September 2012 altercation by the Downing Street gates.
In documents submitted to the High Court, lawyers for PC Rowland justify the claim on the grounds that his reputation has been damaged by Mr Mitchell's remarks and he suffered "great distress, humiliation and upset".
30 April 2014
PC Gillian Weatherley is dismissed for gross misconduct by the Metropolitan Police over leaks to the press about the "plebgate" affair.
21 May 2014
PC Susan Johnson, a Metropolitan Police officer serving with the diplomatic protection group, is sacked for gross misconduct over the press leaks.
6 October 2014
A High Court ruling finds there was no proper final report prepared for the investigation into the three Police Federation officers who met Mr Mitchell. That probe was conducted by West Mercia Police but supervised by the IPCC.
The High Court also quashed the IPCC's decision to investigate the case itself. An IPCC spokesman said it "welcomed" the ruling that the decisions of the three police forces had been "invalid" and said it would make a "fresh assessment" of the case.
3 November 2014
The IPCC again says it is to investigate three Police Federation officers over the "plebgate" affair, having re-assessed the case.
17 November 2014
The libel trial involving Mr Mitchell and former PC Toby Rowland gets under way in the High Court in London. Lawyers for Mr Mitchell tell the court that the police spun a "web of lies" that led to a "vitriolic" campaign against their client.
19 November 2014
Musician and aid campaigner Sir Bob Geldof is cited as a character witness for Mr Mitchell, a former international development secretary. In a written statement submitted to the court, Sir Bob describes Mr Mitchell as a "good man" and "an advocate for the less fortunate", adding that he had never heard him "use the ridiculous and archaic expression 'pleb'".
20 November 2014
A former police officer who was on duty during the "plebgate" incident denies wishing to harm Mr Mitchell or the government. Gillian Weatherley, who was sacked over leaks of alleged details of the row, tells the court that text messages she sent suggesting she could "topple the Tory government" were meant to be sarcastic.
24 November 2014
A police officer who accompanied Mr Mitchell on two foreign trips says the former cabinet minister was "unpleasant until he got what he wanted". Insp Duncan Johnston, who travelled with the then international development secretary in 2011, tells the court Mr Mitchell would "erupt" but later be charming. Separately, two former Conservative whips state in written evidence that Mr Mitchell had been unable to recall the exact words he had used in the days and weeks after the event.
27 November 2014
Former government chief whip Andrew Mitchell loses his High Court libel action. Mr Mitchell had sued News Group Newspapers over the story in the Sun in 2012 which claimed he called PC Toby Rowland a "pleb". Mr Mitchell acknowledged that he had used bad language but maintained he had not used that word. Delivering his ruling, Mr Justice Mitting said he was satisfied that the MP did say the word "pleb"