Boris Johnson follow suit after Thatcher, Major and Heath in facing a leadership vote

Boris Johnson will follow in Margaret Thatcher’s footsteps by facing only the seventh vote of confidence in a serving Tory leader in modern history tonight.

Five past prime ministers have faced the wrath of their backbenchers, with two of them, Ted Heath in 1975 and Sir Iain Duncan Smith in 2003, losing the vote and being forced to resign immediately.

Despite winning, the Iron Lady was forced to retire in 1990 because the margin of victory was so small that she was worried she couldn’t go on.

It’s the second vote of no confidence (Vonc) in less than four years, following Theresa May’s temporary victory over her Brexiteer adversaries in late 2018.

Because the rules governing leadership challenges have evolved over time, it’s difficult to reconcile prior results with current circumstances.

Sir Graham Brady, the head of the Conservative Party’s backbench 1922 Committee, has a vote.

If 15% of Tory MPs write to the chairman, a vote of no confidence must be convened. The current threshold is 54 MPs.

Letters are private unless the MP who sent them makes them public. This means that only Sir Graham is aware of the total number of letters.

A vote is taken, and the leader only needs the backing of a simple majority of MPs to win. In actuality, a decisive victory is required for them to retain their position.