He had piloted a steady course through the ranks to the job of Chief Whip with hardly anyone outside the Westminster village noticing.
Although he was a familiar figure as he cycled around Whitehall on his bicycle with its wicker shopping basket carrying his briefcase, members of the public would not have marked him out from any of the other business commuters and cyclists.
That anonymity was brutally ended in September last year with a front page headline in the Sun which shouted: "Top cop calls for Tory Chief Whip to quit over pleb rant."
The story went on to say : "Cops have called on foul-mouthed Tory Chief Whip to resign after confirming that the millionaire minister launched an f-word rant at armed police."
According to the story, when Mitchell had been prevented by Downing Street police from cycling out of the large main gate, he turned on them by saying: "Best you learn your f***ing place. You don't run this f***ing government.... You're f***ing plebs."
The ensuing storm - finally branded Plebgate, although alternatively known as Plodgate or Gategate - saw Mitchell fiercely denying using the toxic word "pleb" but admitting he had sworn and not treated the police with the respect they deserved.
He finally quit his job on 19 October saying in a letter to the Prime Minister David Cameron: "It has become clear to me that whatever the rights and wrongs of the matter I will not be able to fulfil my duties as we both would wish.
"Nor is it fair to continue to put my family and colleagues through this upsetting and damaging publicity".
Anyone who saw or spoke to Mitchell during those weeks witnessed the pretty dramatic effect it was having on him. He appeared drawn, lost weight and was clearly deeply troubled. He continued to profess his innocence and deny using the word pleb.
Return to top team
A year on and the affair continues to grab headlines but the pendulum has dramatically swung in Mitchell's favour and points towards the police force which is now accused of an extraordinary smear campaign and subsequent cover-up.
Police officers have been arrested, there are claims of fabricated stories about the incident, some officers stand accused of lying about a subsequent meeting with Mitchell and there is a growing suspicion the entire affair was part of a coordinated plot by police, including senior officers, to discredit him and undermine the government with whom they were locked in a battle over cuts.
The prime minister and home secretary have demanded the police apologise to Mitchell for some of their behaviour and there are calls for him to be brought back into Cameron's top team.
One of the most notable elements of the entire affair, however, was the readiness with which many in Westminster lined up against Mitchell when the original story broke.
It is in hard times that you discover who your real friends are, as Mitchell discovered. There were just too many who knew him, including friends and colleagues, who were willing to believe the story and, as a result, unwilling to bat for him.
Former Tory minister Michael Portillo gave the clearest indication of that effect when, speaking on the BBC's This Week show on Thursday night, he said he had heard Mitchell using the toxic word "pleb" in private - it is toxic because it plays into the notion of a government filled with over-privileged, rich, posh boys who treat ordinary mortals with contempt.
"I have heard him use that word in private conversations. I did not believe he could have used it at the gates" Portillo said.
When asked to confirm he had heard Mitchell use the word pleb in private, he added, uncomfortably: "I think I did, but not in a bad context" - quite what a good context might be was left unanswered.
Portillo continued: "Some policeman thought, 'Ah, that is a word that people will believe Andrew Mitchell might have used', But he would not have used it in that context".
And there's the problem. There were just too many people in Westminster who knew Mitchell well enough to believe he would have used the word, even in that context.
Others simply believed, and still believe, that even without using the word pleb, the fact that he had sworn in the presence of police officers doing their duty was enough to require his resignation.
The simple test they apply is what would have happened to any ordinary member of the public had they behaved in the same way to police officers.
There were other stories about Mitchell's general behaviour that played into the picture of him as an unpleasant character.
One colleague recalled how, during a conversation with a mutual friend at a Tory Party conference, Mitchell bounded up, almost physically barged him out of the way so he could talk to the colleague.
"It was as if I wasn't there, as if he hadn't seen me or I was just not important enough to be in his way."
There were one too many stories like this to allow many to give Mitchell the benefit of the doubt.
Other friends did rally to his side claiming that, whatever his faults, they simply did not believe he would have behaved in the way it was being claimed.
Mitchell is the son of former Tory MP David Mitchell and was educated at Rugby School, of Tom Brown's Schooldays and Flashman fame. It was during his time there he won the nickname "Thrasher" because of his tough approach to discipline.
He later served in the Royal Tank Regiment, went to Cambridge to read History and became Chairman of the University Conservative Association and President of the Union between 1978-9.
He first entered parliament in 1987 but lost his seat in the 1997 Labour landslide before returning in 2001 as MP for Sutton Coldfield.
He was given a number of junior ministerial jobs but got his biggest break when he was made shadow International Development Secretary by then-leader Michael Howard.
He ran the unsuccessful leadership campaign for David Davis but kept his job when David Cameron won and kept it in government, where he was widely believed to have been one of the most effective ministers in that post for many years.
However, it was in that role in 2009 when visiting a project in Rwanda that he sparked controversy when he and his aides were alleged to have verbally abused a volunteer who had written a draft newspaper article criticising the way the project was being run.
She claimed Mitchell texted her father, who was a friend from University days, saying the aides "are threatening her with physical violence and I can't say I blame them".
This story and several others about Mitchell's alleged arrogance and snobbery all re-emerged during the height of Plebgate and explained why, when the chips were down, there just weren't enough people ready to leap instantly to his defence.
Unfortunately for Mitchell, he had a reputation for making enemies all to easily and friends with difficulty.
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