The Sutton Coldfield MP sued News Group Newspapers (NGN) over a September 2012 story in the Sun which he said meant he was guilty of launching a grossly offensive and arrogant attack on Downing Street police officers who refused to allow him to cycle through the main vehicle gates, branding them “f****** plebs”.
NGN based its report, which it said was substantially true, on the account given in his log by Pc Toby Rowland.
Giving his ruling, Mr Justice Mitting said: “For the reasons given I am satisfied at least on the balance of probabilities that Mr Mitchell did speak the words alleged or something so close to them as to amount to the same including the politically toxic word pleb.”
The officer claimed statements made by the 58-year-old MP for Sutton Coldfield from December 2012 onwards falsely suggested he had fabricated his allegations.
But Mr Mitchell, who resigned as whip a month after the altercation, denied saying: "Best you learn your f****** place - you don't run this f****** government - you're f****** plebs."
He said he would never call a policeman a pleb "let alone a f****** pleb" - although he agreed he muttered audibly under his breath 'I thought you lot were supposed to f****** help us' - but not at the officer.
He was in a hurry to get to the Carlton Club that evening and was expecting to be let through as he had been without difficulty that morning and after lunch.
He thought it "extremely odd" when Pc Rowland issued him with a warning under the Public Order Act, but apologised to the officer for his language the next day.
Mr Mitchell agreed that the chief whip's role required a mixture of charm and menace and that he could occasionally be abrasive, but said he did not merit the "extraordinary tsunami of vitriol which descended on my head over a prolonged period of time".
His counsel, James Price QC, said a "web of lies, deceit and indiscipline" by police officers led to a press campaign and public hostility and the version of the encounter which was leaked to the newspaper by a number of officers was "wholly false".
Mr Price said: "In the end, the lies brought Mr Mitchell down, destroying a political career of 27 years."
Statements supplied in court by a range of people, from musician Bob Geldof to painter and decorator Richard Robinson, showed he was not a "Tory toff", who would think of putting someone down because of their class, social background or occupational status by use of a "toxic and class-laden" expression like pleb.
But Desmond Browne QC, for Pc Rowland, claimed Mr Mitchell was a "Jekyll and Hyde" character whose capacity for menace found its outlet in foul temper and foul language.
He said the MP was regularly let through the vehicle gates, in the face of the security policy, because of the "unpleasant fuss" he made.
Pc Rowland said he did not know who Mr Mitchell was when he saw the "agitated" MP having a disagreement with a fellow officer and went to speak to him.
"I was perfectly calm, perfectly polite. It is quite common to have disagreements about entrances and times people can come and go."
He claimed that members of the public were within earshot and visibly shocked when Mr Mitchell swore, which prompted the "correct, proportionate and very necessary" warning.
He denied that his account was an invention to "cover my arse" and justify giving a Cabinet minister a warning, maintaining that he recorded exactly what happened when it was fresh in his mind.