Boris Johnson confronted the fear that further Conservatives may defect to UKIP, and used humour to vanquish it. He began his annual speech to the ConHome rally by expressing a regret: never once has he had so much as “a soupçon… of a suggestion that I should defect to another party”.

Despite the Mayor of London’s astonishing achievements since 2008, which apparently include extending the life expectancy of Londoners by one-and-a-half years, “Ed Miliband has never thought to invite me to join Labour, even though he and I went to the same school” – a reference to the fact that both men attended Primrose Hill Primary School.

And there has been “not a peep from the Liberal Democrats, not a peep from the Clegger”. Nor has the planting of 10,000 trees, and reduction of CO2 emissions by about 20 per cent, led to any “wooing from the Greens”.

“Is there any other party that anyone can think of?” the Mayor demanded. UKIP, came the reply. Boris proceeded to disclose that he had met Nigel Farage in a pub about 20 years ago, and had urged him to join the Conservatives, an offer which he intends to repeat the next time he meets the UKIP leader.

All this was received with rapture. Here is a Conservative who is itching to go out and bring back the lost UKIP sheep, and who makes it sound like the most natural and feasible plan in the world.

The Mayor dilated at some length on the many wonderful things that are happening in London, and the way these benefit the whole country. But he could not pretend to have removed all dangers: “I can’t guarantee you won’t be accosted in a park by Ed Miliband in search of inspiration.”

One way to defeat UKIP is to proclaim a robust Conservative approach to the renegotiation of our relationship with Brussels. “We all want reform, don’t we?” Boris demanded, and alluded to the recent report that the European Union is trying to make us use less powerful vacuum cleaners.

He admitted that some people do present themselves at A&E with “barely credible injuries sustained in what I can only call vacuum cleaner abuse”. But it is not for the EU to tell us how powerful our vacuum cleaners are to be. We are more than capable of deciding that question for ourselves. And “isn’t it fair enough” for us to control the number of people who come to live in this country?

Someone had claimed that the present situation had “echoes of 1997”. This, Boris pointed out, was ridiculous. He and Paul Goodman could remember fighting the general election campaign of 1997. The Conservatives were then 20 points or more behind in the polls. The present deficit is nothing like that. He suggested the situation is much more like 1983, when the Conservatives came from behind to win a convincing victory. He himself came from behind in 2008 to win the mayoral election in London.

Boris embarked on a final analogy. The Conservative plane is on the runway. It’s picking up speed, the nose is coming up and “Balls and Miliband in their clapped out jalopy” can be seen making a desperate but doomed attempt to stop it taking off.

This image enabled the mayor to add that “by the way, it’s the moment to give us the aviation capacity we so desperately need”. The hall rose to cheer him. This was not one of those polite standing ovations, given to a minister reluctant to leave the stage without exacting such a tribute. It was an enthusiastic tribute to a speaker who had helped to restore his audience’s self-belief.