What next for Boris Johnson?

Following a spectacular fall from grace and power, speculation is rife about what outgoing British Prime Minister Boris Johnson will do next.

Will he plot a comeback from the backbenches in parliament or cash in and wreak revenge as a political pundit?

Johnson, 58, famously signed off his final performance as prime minister in the House of Commons by telling MPs: "Hasta la vista, baby".

He may as well have used another line from the "Terminator" films -- "I'll be back" -- as it only fuelled speculation that he has unfinished political business.

Allies said he wants to lead the Conservative party at the next general election, due in two years time, even though a new leader will be crowned on September 5.

"I suspect he's not totally given up on the idea of a comeback," politics professor Tim Bale, from Queen Mary University of London, told AFP.

"I suspect friends of Boris Johnson... will be talking to journalists off the record all the time and criticising, albeit not openly, his successor."

Despite being ousted by his own MPs following a string of scandals, Johnson remains popular with many party members.

According to Daniel Bowman, a political researcher at the University of Liverpool, he could leverage that power to settle some scores.

"Boris Johnson is a well-known agitator. I think revenge may be on his mind," he said.

This could be as a member of the cabinet, he said, pointing out that Liz Truss, the favourite to succeed him, had not ruled out giving Johnson a ministerial role.

"He could also be an agitator on the backbenches," said Bowman.

Whoever takes over will immediately face the task of tackling the soaring cost of living and rampant inflation and is likely to hear calls for a general election to legitimise their power.

Should he stay on as a rank-and-file MP, Johnson could make mischief for his successor, as his predecessor Theresa May did for him.

It would also be the ideal position for him to lie in wait in case his replacement is felled.

But that choice may not be entirely in his own hands.

Parliament's Privileges Committee is due to report on whether he committed "contempt of the House of Commons" by saying that he believed no lockdown rules were broken in his Downing Street office.

Johnson, wife Carrie and leadership candidate Rishi Sunak, whose resignation as finance minister triggered his eventual demise, received fines for attending a birthday celebration in June 2020.

He risks losing his seat if the committee rules that he should be suspended from parliament, triggering a by-election at a time when the ruling Conservatives trail dismally in the polls.

Even if he survives the investigation, Bowman said Johnson may quit parliament anyway, if Labour look set to take the next election and he loses his seat.

"So maybe he might acknowledge that actually his political career, his time is running out, and he will be better on the sidelines, using the power of the media" to realise his ambitions, said Bowman.

Having reportedly complained that he was struggling to make ends meet on his ?164,000 ($193,000) prime ministerial salary, Johnson could accept lucrative offers to become a columnist or a pundit.

His former employer The Daily Telegraph and the popular conservative newspaper the Daily Mail are both likely suitors.

According to the parliamentary register of members' interests in 2018, Johnson was paid ?275,000 a year to write a weekly column in the Telegraph.

As a former prime minister, he would likely command even more money.

"I think Boris Johnson will inevitably go to the highest bidder," said Bowman.

His predecessor May, not known for her rhetorical flair, earned more than ?1 million in speaking fees in the year after she left office in 2019.

Otherwise, he could become a multi-millionaire by writing his memoirs and joining the international lecture circuit, with the ability to command around $100,000 per speech in the United States, Mark Cowne, CEO of the Kruger Cowne agency, told AFP.

A newspaper job would give Johnson a platform to attack those he blames for his downfall and make a case to become leader again.

"I really think he'll pull all the levers he possibly can and really try to talk to his base," said Bowman.

"Outside of parliament, he really has the ability to construct his own narrative and his own attack line."

Either way, he is likely to cause his successor "a lot of trouble", he predicted.