Whoever becomes the next Prime Minister will have a big Boris Johnson-shaped problem to deal with on their first day in office.
As former party leader William Hague pointed out, the shamed PM is likely to be a thorn in the side of whoever succeeds him.
Those close to him suggest he is plotting a comeback, and his now-famous "hasta la vista" signoff at PMQs last week has done little to put these rumours to bed.
Despite being unceremoniously dumped by his party, Mr Johnson isn't without his supporters, with some loyalists calling on the Tories to let him stay on.
No10 has stressed the PM will leave office on September 6, but his plans beyond that are unclear.
Free of the constraints of office, he could make a nuisance of himself from the backbenches, or outside Parliament altogether.
Last night both Liz Truss and Rishi Sunak said they would not be offering him a role in his cabinet - and questioned whether he would want one.
But given his fondness for master of reinvention Winston Churchill - who Mr Johnson has penned a book about - it is not beyond the realms of possibility that he is working out a path back to power - and that's a very dangerous prospect indeed for Mr Sunak or Ms Truss.
Here are some of the things that could happen next.
Boris Johnson is allowed to continue as Prime Minister
Let's be honest, this is not a likely outcome.
It would be quite the U-turn if the Tories opened the door for him to remain in post after he was unceremoniously dumped by his own MPs following a string of scandals.
But those who know him suggest Mr Johnson hasn't given up the ghost, even as would-be successors kick lumps out of each other in a bitter leadership contest.
Lord Cruddas of Shoreditch, a former Conservative Party treasurer, told the Telegraph, Mr Johnson "wants to fight the next general election as leader of the Conservative party".
The peer has organised a petition calling for Mr Johnson to carry on as Prime Minister.
More than 10,000 Tory members have signed it, demanding his name be added to the ballot when members vote for a new leader next month.
But Downing Street has poured water on the suggestion, with a No10 spokeswoman stating: “The Prime Minister has resigned as party leader and set out his intention to stand down as PM when the new leader is in place.”
He plots a Churchill-style comeback from the backbenches
The PM knows he's popular at the ballot box - or at least he used to be.
The majority of Tory MPs might be against him now, but will that be the case if they take a hammering in the future?
It's entirely possible that Mr Johnson could bide his time on the backbenches until an opportunity presents itself to sweep in and try resurrect their prospects.
He will no doubt have his professed idol, Winston Churchill, in mind if he spends time in the "wilderness".
The wartime leader, who was swept from office by the electorate in 1945 but returned triumphantly in 1951, is likely to be an inspiration to the current PM if he opts for this path.
Churchill was in and out of government, and even out of Parliament, for decades before he got his two opportunities to lead the country.
Liz Truss and Rishi Sunak both claim the other will lead the party to defeat at the next General Election. If they prove correct, and the Tories do end up in opposition, it is entirely possible that there could be another leadership race.
If this happens, Mr Johnson may well fancy his chances at leading the party, and after a spell away from the cut-and-thrust of government might be able to convince his party that he's a reformed character.
Churchill was, after all, the master of reinvention, and few have studied him in more depth that Mr Johnson, who has even penned a biography of the famous leader.
Lord Hague pointedly wrote: "Boris lives his life as a performance, and he will want the next act to fill every seat in the theatre of British political life."
He could be given a Cabinet role
There's a lot up in the air here. Both the candidates last night said they would not be offering Boris Johnson a role within their Cabinet, suggesting his time has passed.
But how attractive will it be to have Mr Johnson causing trouble on the backbenches?
As soon as he leaves office the PM will likely be inundated with offers as a columnist or pundit, and his successor can be forgiven for not wanting such an outspoken figure breathing down their neck.
Might they, after all, decide it's better to bring him into the fold rather than have him making a nuisance of himself outside?
This may have been part of Theresa May's thinking when she surprisingly appointed Mr Johnson as Foreign Secretary shortly after she took office in 2016.
Just as Mrs May has proved to be a thorn in the PM's side from the backbenches - asking difficult questions and seemingly refusing to clap him in the Commons - so Mr Johnson could be a problem the next PM could do without.
That said, it remains to be seen whether the current Tory leader would accept a cabinet role if it was offered. The prospect of not being bound by collective responsibility after the party rounded on him might be an attractive one.
He retreats gracefully and steps down as an MP
This is the route the majority of Prime Ministers take. Tony Blair and David Cameron did not stick around in the Commons long after they stepped down from the top job, and Mr Johnson could decide to do the same.
As has been widely pointed out, there's a fortune to be made in the private sector, and it possible he will resume writing his book about Shakespeare once he has more time on his hands.
At 58, the PM has plenty of time to amass some serious wealth in whatever venture he does next, having reportedly claimed he was struggling to make ends meet in No10.
He is likely to get a lucrative newspaper column when he leaves No10, which would help him to remain a big presence in British politics.
The Telegraph paid him £250,000-year to write for them - a sum he famously described as "chicken feed", while his dogged backers at the Daily Mail could also hire his services.
Mr Johnson is thought to be considering the speaking circuit, where he could command massive fees for speeches in the Middle East, Asia and the US.
He needs to finish his long-delayed biography of Shakespeare and could even write a book about his time in office.
Tony Blair was paid millions for his memoir but he donated it to the Royal British Legion. Mr Johnson is unlikely to follow the same course.
It remains to be seen whether the draw of power will continue its hold on him, or whether he decides to walk away into the sunset.
But it's worth observing that quitting Parliament doesn't have to be the end. Let's not forget that Churchill was in and out of the Commons, notably after losing his seat in 1922.
Even if he does decide not to stand again in the next election - or even if he steps down beforehand - it might not be the last we've seen of Alexander Boris de Pfeffel Johnson in Parliament.
