She heads home to find hardcore Tory Brexiteers threatening to help the Labour party bring down her government, cabinet ministers being urged to oust her, and members of her top team preparing for a “people’s vote”.

Publicly, Downing Street’s first-choice scenario is still to secure some form of clarification from Brussels on the backstop, the so-called insurance policy that is the most contentious part of the withdrawal deal, and then put it to a vote in the Commons in January.

But, after 117 Tory MPs declared they had no confidence in the PM this week, May’s aides privately accept that is an unlikely path to victory.

According to sources in Whitehall, their main fear is that Labour will call a confidence vote in the Commons — either as soon as next week or immediately after the Brexit deal is rejected by parliament — and that a rump of hardline Tory Brexiteers will then abstain, defeating the government.

Sources in the government and the pro-Brexit European Research Group agree there is a hardcore group of at least 20 MPs who are seriously talking about abstaining in the event of a confidence vote, in the hope of forcing a change of leader. They are said to believe an emergency Tory leadership contest could be held in 14 days to anoint a new Brexiteer PM.

This group of Eurosceptic rebels has been branded a “suicide squad” by Tory colleagues.