He started the day before dawn with a run, apparently wearing his white shirt from the day before, and finished it looking more than ever like a contender for the Conservative leadership.
In a wildly applauded speech, he mentioned the Prime Minister only in passing, called him "Dave", and never uttered the name of the Chancellor, George Osborne, his most obvious rival in a future leadership contest.
He fired several warning shots about the impact of Government policy on London's prosperity. Pointing out that an order to supply London's rail transport system was keeping 187 people in work in a Manchester factory close to where the Conservative conference is being held, the Mayor said: "I will not allow that investment to be jeopardised for short-term political gain."
He added: "I say to my friends in the Treasury – not all of whom I see here; well, Dave's here – you help us to invest in London Transport and we'll supply the locomotive of the UK economy."
Mr Osborne was not in the audience, though the Prime Minister, who had managed not to cross paths with the Mayor during his morning run, was.
Mr Johnson has previously criticised the Government's decision to cut police numbers, as part of a Treasury-led drive to bring down public spending. He opened yesterday's speech with a promise: "I will not allow police numbers to fall below a level that I believe is safe or reasonable."
The Mayor hinted at his long-running argument with the Government over the 50p tax rate, which he believes makes London less competitive than foreign cities. He told representatives: "Get the right tax and regulatory framework – and I will say no more than that – then British enterprise will do the rest."
Interviewed on BBC's Newsnight last night, he said: "I think there are people in the Treasury who understand that the arguments in favour of higher taxes are not very well made out."
Mr Johnson promised cheering conference delegates that he will protect London from Government-imposed spending cuts, as the Mayor's close allies said that while his immediate ambition is to be re-elected, it will not stop him making an early return to the House of Commons to be in position to contest the party leadership.
But Mr Johnson ruled out becoming an MP again before 2016 if he is re-elected as Mayor. "There is not a snowball's chance in Hades," he told Newsnight. He added that "when seeking a mandate, that would be wrong".
Mr Cameron joined the standing ovation for Mr Johnson's speech, though the previous evening they both made jokey references to a rivalry that goes back to their time at Eton College and Oxford University.
At a reception on Monday, Mr Cameron made an oblique reference to a revelation in a recent biography by Sonia Purnell that Johnson had once called him a "cunt". He remarked: "I don't know a four-letter word to describe Boris."
Mr Johnson told a party rally soon afterwards: "You all know that there are some embarrassing truths that you can't really escape as a politician. I've got a confession. I was at the same school as the party leader. There we were at this antiquated redbrick establishment... with green fields of exceptional lushness. It's absolutely true. I was at the same north London primary school as Ed Miliband."
Though Mr Johnson's performance delighted the Tory faithful, others were less impressed. Labour's Ken Livingstone, who will be Mr Johnson's main challenger in next year's mayoral race, said: "Today we saw the real Boris Johnson – an out-of-touch Conservative, failing to put ordinary Londoners first on the issues that really affect them, from rising fares to police cuts.
"Under the Conservatives, Londoners are less well off and increasingly less safe, under a moonlighting mayor who meets bankers more than the police. People in London are feeling the squeeze but Boris Johnson doesn't see it."