Boris Johnson stood at a crossroads on Wednesday night after he was forced to apologise to the country for his attendance at a Downing Street garden party.

His administration faced further scrutiny on Thursday after it emerged that two leaving parties for No 10 staff were held on the eve of Prince Philip’s funeral, with Downing Street later issuing a formal apology to Buckingham Palace.

As Tory MPs began to send in their letters of no confidence to Sir Graham Brady, the chairman of the 1922 Committee, Westminster speculated on what could happen next for the Prime Minister.

Will Sue Gray’s inquiry into the No 10 gatherings exonerate him? Will his backbenchers support him? And will he see out the year?

Here are six scenarios that could come next.

Boris Johnson is replaced

Sue Gray’s investigation concludes that gatherings in Downing Street should not have taken place and that Boris Johnson knew they were happening at the time. The Metropolitan Police launches a criminal investigation, using Ms Gray’s evidence from civil servants to prosecute staff who broke the rules.

The incident sends the Conservatives’ polling performance into terminal decline, prompting the critical mass of 54 MPs to send their letters of no confidence to Sir Graham. Mr Johnson does not make it onto the final ballot and is replaced as Prime Minister by the summer.

Prime Minister clings on – just

Boris Johnson is slapped on the wrist by Sue Gray’s inquiry, which concludes that he should have done more to ensure that his staff followed the lockdown rules. The Metropolitan Police sticks to its line that officers do not investigate historic allegations of Covid regulation breaches.

The Prime Minister uses up the last of his nine lives with Tory backbenchers, who are already angry about policy U-turns, a rise in National Insurance and the effect of the cost of living crisis on their constituents.