Boris paves way for Tory leadership challenge with plan for comeback as Henley MP

Boris Johnson is preparing an extraordinary comeback as MP for his old constituency of Henley, paving the way for him to fight a leadership election during the next parliament, under a plan being drawn up inside his camp.

The Mayor of London went to war with David Cameron last week, criticising what he called a "fudgearama" over Heathrow airport, overshadowing the Prime Minister's reshuffle and fuelling speculation that he will challenge for the Tory leadership after the next election.

Mr Johnson's allies last night insisted he would serve his "full term" as mayor until 2016, but after that would be ready to stand in a by-election. And a separate source inside the Henley constituency said that the former MP would be "welcomed back with open arms" to the Tory safe seat.

A friend said: "Boris has had a gold-medal Olympics. He will concentrate on being mayor for a full term and will try and convert those that doubt he is a serious politician. Any constituency would want him, although he has a house in Henley."

It has been suggested that Mr Johnson could stand in a by-election in Richmond Park, south-west London, if the Conservative Zac Goldsmith resigned in protest over the Government's plans to expand Heathrow. But Mr Goldsmith's 4,091 majority is regarded as not safe enough compared with Henley, where Mr Johnson's successor, John Howell, has a majority of 16,588.

One theory is that Mr Johnson would complete his four-year term as mayor in 2016 and put himself forward for a by-election that year. If Mr Cameron lost the 2015 election, he could stand aside as Tory leader, triggering an immediate leadership race which would exclude Mr Johnson. However, if he remained leader in opposition, giving his potential successors time to build up support, there is growing speculation in Tory circles that the leadership race would be in 2018.

But the Henley plan will no doubt be of surprise to Mr Howell, who is not standing down.

In the wake of the reshuffle last Tuesday, Mr Johnson launched a frontal assault on Mr Cameron after the PM moved the Putney MP Justine Greening from her job as transport secretary to International Development, in the clearest signal yet that a third runway is back on the table.

He condemned the setting up of a review into airport capacity in the South-east, headed by the former CBI boss Howard Davies, as it would not be completed for three years.

Asked whether he would fight a parliamentary by-election against Heathrow expansion, Mr Johnson said, cryptically: "My job is to follow the interests of the people of London. I was elected on a very clear mandate to oppose the third runway at Heathrow – expansion of Heathrow – that, indeed, is the mandate on which this government was elected, and that's what I'd like to see and do."

Downing Street retaliated by briefing a veiled warning to Mr Johnson: "We will see what happens the next time he comes around with the begging bowl. He might need us one day."