Boris Johnson believes that he has unfinished business in 10 Downing Street.
We know this because, just weeks after resigning from “the best job in the world”, he tried to get it back.
Despite managing to get the support of more than 100 Tory MPs - the minimum requirement to get on the final leadership ballot - Johnson decided to bow out of the contest at the last minute.
“You can’t govern effectively unless you have a united party in parliament,” he said.
His analysis was correct, and applies just as much to Rishi Sunak as it did to Johnson himself.
Barely two months after taking over from Liz Truss, Sunak finds himself leading a parliamentary party still at war with itself – with Johnson and his supporters determined to make life as difficult for him as possible.
This has led to speculation that the former PM could return to Number 10 as soon as this summer, should things go badly for the Conservatives in May’s local elections.
A disastrous showing for the party could, the argument goes, force MPs with more than one eye on the next general election (expected in 2024) to oust Sunak and turn once again to the man who led them to a landslide victory in 2019.
Leading the charge for the Borisites is Lord Cruddas, a former Tory party treasurer who was ennobled by Johnson and regularly criticises Sunak on Twitter.
Alongside Johnson’s former home secretary, Priti Patel, Cruddas has formed the Conservative Democratic Organisation in an attempt to give greater power to Tory party members – most of whom still support the former leader.
Borrowing Johnson’s famous Brexit referendum phrase, the Tory peer said: “Our key aim is to put us, the members, back in the driving seat – to ‘take back control’.”
Nadine Dorries, another leading member of the Johnson fan club, has also made her unhappiness with Sunak clear.
The prime minister has, she claimed this week, washed Johnson’s legacy “down the drain” by ditching so many of his signature policies.
Lord Greenhalgh, who was also made a Tory peer by Johnson, told Newsnight there was a “strong probability” his friend and ally will be back in Number 10 by the end of the year.
Adding to the intrigue is the fact that Johnson has announced he intends to stand again in Uxbridge at the next election rather than quitting parliament altogether like former PMs Tony Blair and David Cameron.
Paul Goodman, the former Tory MP and now highly-respected editor of the ConservativeHome website, wrote in The Times that he believed a Johnson comeback was unwise – but cannot be ruled out.
“The return of Boris Johnson to No 10 this year has a certain plausibility — at least to his Westminster supporters,” he wrote.
Writing in the New Statesman, former cabinet minister David Gauke – no fan of Johnson – admitted that the idea he could return this year “is gaining momentum”.
″The more one thinks about it, the less incredible a Johnson return appears,” he said. “We might not be done with him yet.”
‘Dead in the water’
Others, however, believe the prospect of Johnson returning to the top job is a non-starter.
“He’ll maybe try, although I doubt it,” one former cabinet minister told HuffPost UK. “But his chances of succeeding would be nil.”
Another senior Conservative is even more forthright.
“The Tory party would be dead in the water if it gets rid of another leader,” they said.
One Conservative insider pointed out that Johnson is “making a lot of cash right now on the rubber chicken circuit and that would have to stop” if he re-entered No10.
They added: “Why on Earth would he want to come back and try and piece together a broken party in the dying days of a parliamentary term and end up as leader of the opposition?
“But I suppose it’s a nice distraction for those diehard Boris supporters from the dire situation we are in.”
Boris Johnson on the day he left 10 Downing Street in September.
An MP who has backed Johnson in the past called on the former PM to back the current man in the job.
“Boris could have stayed in the leadership race having met the votes’ threshold but he wanted to come back with overwhelming acclamation, like a coronation, but that didn’t happen and he pulled out of the leadership race, leaving many supporters crestfallen and disappointed,” the backbencher said.
“If he comes back as leader of the party, it’s likely to be after the next election and not before, but only if he gives full support to Rishi winning the election.
“Anything short of that could be his undoing and not forgiven even by those who support him.
“He needs to bury any ill will towards Rishi, and be seen as the most loyal MP on the backbenches if he wants to try and become PM again, whenever that might be.”
Others speculate that Johnson may even have his eye on another of his former jobs.
“He can maybe go back to being mayor of London and be popular again,” said one source.
Whether he makes another comeback bid or not, the mere presence of Johnson on the backbenches will continue to dog Rishi Sunak, no matter how long he remains PM.