What time is the vote of no-confidence in Theresa May and will she survive as prime minister?

Theresa May is set to face a no-confidence vote from her own party on Wednesday evening over her handling of Brexit.

The chairman of the 1922 Committee of Tory backbenchers, Sir Graham Brady, has announced he has received letters expressing disapproval of Ms May from more than 15 per cent of MPs (meaning 48 at present). Passing this threshold obliges Sir Graham to trigger a no-confidence ballot of party members on the prime minister’s future.

The scales have finally been tipped against Ms May after she cancelled a “meaningful” vote on her EU Withdrawal Agreement, due to take place in the House of Commons on Tuesday, in order to return to Europe to seek further concessions from EU leaders, apparently without success.

The development is embarrassing for the embattled prime minister on a personal level, given that she has fought doggedly to deliver Brexit despite widespread dissatisfaction with her terms, vocal Remain opposition, campaigns for a second referendum and the resignation of several key cabinet ministers.

If the prime minister survives the new vote – taking place between 6pm and 8pm tonight – place and sees off a leadership challenge, she would be rewarded with a year’s immunity from a fresh coup attempt under the rules of the 1922.

But if she were to lose, she would be obliged to step down and allow for the election of a replacement, once again plunging Westminster into chaos, a circumstance she has emphatically cautioned against.

Even if she were to win the initial battle, however, she could still lose the war. If a large enough minority of MPs vote against her – 100 is thought to be in the region of the magic number – then her cabinet may advise her to step down anyway.

Under Sir Graham, a no-confidence letter is held on file indefinitely once submitted, unless the author asks for it to be withdrawn. Previously, they would have had to renew their objection on an annual basis.

To prevent disgruntled members conspiring against their boss in cloak-and-dagger fashion, the process is a blind one, with only the committee’s chairman knowing for sure how many letters have been submitted at any one time.

The 1922, which meets in Parliament’s oak-panelled Committee Room 14 at 5pm every Wednesday afternoon, is named after the historic Carlton Club meeting between Tory rebels Stanley Baldwin and Bonar Law on 19 October 1922, in which the men successfully plotted the withdrawal of the party from its coalition with David Lloyd George’s Liberals.

Initially a private dining club, “the men in grey suits” have enjoyed their reputation for organised dissent ever since.

They wield considerable power. The prime minister is expected to appear before its assembled members to give an account of themselves at least once a quarter and whenever a significant political event takes place.

All six most senior members of its executive – Sir Graham, Cheryl Gillan, Charles Walker, Bob Blackman, Nigel Evans and Geoffrey Clifton-Brown – voted for Brexit.

The sextet, which gathers an hour before the midweek huddle, is unlikely to back Theresa May any further if they do not agree with her plans for Britain’s exit from Europe and could become dangerous enemies.