MPs are due to vote today on whether Heathrow should get a third runway.

One of the most vocal opponents to the policy is Boris Johnson, whose Uxbridge constituency is right under the flight path of the west London airport. Back in 2015, he pledged to “lie down in front of those bulldozers” to stop the expansion.

So you can imagine his colleagues’ surprise when it was announced that the foreign secretary would not be in the country for today’s momentous vote. The transport secretary, Chris Grayling, told Radio 4 this morning that he had “no idea where Boris is.”

As the long-awaited Heathrow project prepares for landing, let’s take a look at what Mr Johnson and others have said about it over the years…

Boris Johnson

Mr Johnson was an outspoken critic of Heathrow expansion throughout his time as Mayor of London. In December 2013, he told reporters that a third runway “would be a mistake.”

Fast-forward to September of the following year, when he penned a piece for the Telegraph, declaring: “There is no government in the Western world that would even contemplate an act so self-defeating, so short-termist, and so barbarically contemptuous of the rights of the population.

He went on: “That is why all three main parties have correctly ruled out expansion of Heathrow airport, in the form of a third runway.” Mr Johnson used the same piece to argue for a brand-new airport in the Thames Estuary, dubbed Boris Island. The project never took off.

In May 2015, Mr Johnson returned to the House of Commons. In his acceptance speech on his election as MP for Uxbridge, he promised: “I will lie down in front of those bulldozers and stop the building, stop the construction of that third runway.”

But just a few weeks later, Mr Johnson appeared to distance himself from the pledge: in July 2015, he suggested “I don’t think my services as a bulldozer blocker will be required, for decades, if ever.”

The strong rhetoric returned in 2016, when, in his first comments on the issue as foreign secretary, he dismissed Heathrow expansion as a “fantasy” and said plans for a third runway should be “consigned to the dustbin.”

Earlier today, it emerged Mr Johnson was in Afghanistan – approximately 3,500 miles from the House of Commons – and would be unable to make it back for the crucial vote.

Theresa May

Mr Johnson is not the only senior government figure in a tricky situation over Heathrow. Theresa May’s own constituency of Maidenhead is just down the road from the airport.

now-deleted post from her website reveals the prime minister’s history of opposing the third runway.

In 2008, when Mrs May was shadow leader of the Commons in David Cameron’s front bench, her constituency site said: “Theresa is firmly against plans to build a third runway at Heathrow Airport and is campaigning against it on behalf of Maidenhead residents.”

The post included a quote from Mrs May: “The Government’s case for expanding Heathrow is flawed… I am clear that we must say no to a third runway at Heathrow.”

In January 2009, the post was updated to cover her campaigns: “Theresa has spoken out against the Government’s plans to build a third runway at Heathrow Airport… Theresa said: ‘I know from all the letter and emails I get that many local people will be devastated by the Government’s decision.’”

But in October 2016, the Conservative government led by Mrs May announced that it would endorse the verdict of the Airports Commission – who had been tasked with investigating the different options for airport expansion. This effectively gave the green light to a third runway at Heathrow.

The 2017 Conservative manifesto included a commitment to expand the airport, and today, Mrs May’s government issued a three-line whip to Conservative MPs to vote for the policy.

David Cameron

Though he’s no longer an MP, it would be wrong to ignore David Cameron’s contribution to the Heathrow debate.

In October 2009, while he was still the fresh-faced leader of the opposition, Mr Cameron told residents of Richmond that the third runway “is not going ahead, no ifs, no buts.”

Apparently to reiterate the pledge, he sponsored the planting of an apple tree that same year in the village of Sipson – just a mile from the perimeter of Heathrow.

But rather like Mr Cameron’s commitment to blocking Heathrow expansion, the tree has since withered, and the field has been cleared.

In June 2012, he seemed to soften his language. Asked by Zac Goldsmith for assurances that there would be no “policy shift” over the government’s then-position against Heathrow expansion, he said: “The coalition position has not changed.” But he warned that the government “mustn’t be blind” to the need to expand airport capacity.

That year, Mr Cameron’s government established the independent Airports Commission to work out how and where to expand the UK’s airport capacity.

In the Conservative manifesto of 2015, the party pledged to respond to the final recommendation from the Commission. Some commentators said this was a way for the government to avoid taking the decision directly.