Plebgate reaches the High Court today when a libel judge will investigate the Downing Street encounter between former Government chief whip Andrew Mitchell and Pc Toby Rowland.
Over two weeks, Mr Justice Mitting, sitting in London without a jury, will hear from both sides as he decides the preliminary issues of the meaning of the words complained of and whether they were substantially true.
There will also be a number of other witnesses, including experts in phonetics and field of vision analysis, and a site visit to Downing Street.
Mitchell is suing News Group Newspapers (NGN) over a September 2012 story in The Sun which the MP says meant that he was guilty of launching a grossly offensive and arrogant attack at Downing Street police officers two days earlier, branding them "fucking plebs" and "morons".
NGN argues that the article was substantially true and, at the heart of its case, is the account given by Pc Rowland.
He claims that Mitchell, having demanded but been denied the right to leave on his bicycle by the main Downing Street gates, lost his temper and said: "Best you learn your fucking place – you don't run this fucking government – you're fucking plebs."
The 58-year-old MP for Sutton Coldfield, who resigned as whip a month after the incident, denies "demanding" to be allowed to use the main gates, losing his temper or using the words attributed to him – although he admits swearing.
He says that he asked politely to use the main gates and muttered under his breath "I thought you guys were supposed to f**king help us".
Both sides agree that Pc Rowland, who is with the Met's Diplomatic Protection Group, heard Mitchell swear and issued him with a verbal warning that if he did so again, he would be arrested.
At the same time, Pc Rowland is suing Mitchell over statements he made in the media from December 2012 onwards and at a press conference in November 2013.
The officer complains that Mitchell accused him of fabricating allegations and evidence against the MP while the officer denies that he has done any such thing. The essence of Mitchell's defence is that what he said was true.
Apart from MItchell's resignation, the fall-out from the affair included the criminal conviction of one officer for misconduct in public office and disciplinary proceedings leading to the dismissal of three other officers.