Ironically, it was his greatest political achievement which fatally undermined his long-held ambition of leading his party and the country.
His sombre demeanour at the press conference called to declare victory in the EU referendum tipped some Westminster observers to think that perhaps the former mayor was realising that Brexit might not be the stepping stone to Number 10 that some assumed.
Commentators suggested that Mr Johnson may have neither expected nor wanted Leave to win, calculating that a narrow defeat would make him the darling of the Eurosceptic right and put him in pole position to succeed David Cameron in a few years, while victory might burden him with the responsibility for plunging the UK into a period of potentially vote-losing instability.
A glimpse into the backroom machinations within his camp emerged when Michael Gove’s wife inadvertently leaked a private email telling her husband to “be your stubborn best” in negotiations with the former mayor over the role he would play in his campaign and his cabinet.
Mr Gove’s shock announcement of his own candidacy pulled the rug from under Mr Johnson’s campaign with a brutally personal assessment that the Uxbridge and South Ruislip MP “cannot provide the leadership or build the team for the task ahead”.
The prospect of fighting his Leave colleague head-on for a place on the ballot paper, coupled with the realisation that he had left himself vulnerable to attacks during the leadership campaign, seem to have prompted a decision to step back from the contest which until that morning he seemed certain to win.
For a man who once claimed there was more chance of him being “reincarnated as an olive” than taking the keys to No 10, Mr Johnson, 52, did a remarkable job of making himself appear the inevitable successor to Mr Cameron.
After leading the Brexiteers to victory, his stock among the widely Eurosceptic Conservatives grassroots was higher than ever and a string of MPs had already thrown their support behind him.
However, Tory colleagues in the Remain camp always suspected the Old Etonian was not an ‘outer’ at heart and many believed he threw his allegiance behind Leave to give himself the best chance of taking over from ‘frenemy’ Mr Cameron.
His election to City Hall in 2008 and retention of the powerful position four years later was a clear demonstration of Mr Johnson’s star quality at the ballot box, catapulting him into the front rank of contenders for the Tory leadership.
His sometimes elusive relationship with the truth led to him being sacked from The Times for inventing a quote and dumped from the Tory frontbenches for lying over an alleged affair.
In an uncomfortable TV grilling in 2013, he was accused by interviewer Eddie Mair of being a “nasty bit of work” over allegations that he promised to help a friend’s plan to have a journalist beaten up.
A stint at the Daily Telegraph as its Brussels correspondent honed his EU-bashing skills but saw him accused of myth-making as he set off a string of warnings about the EU’s supposed attempts to ban bendy bananas or prawn cocktail crisps.