Boris Johnson gave his strongest hint yet of a planned return to frontline politics as he likened himself to a Roman statesman who was called back for a final battle.

Friends of the departing prime minister, including loyal MPs, said Johnson was holding out hope of a return to No 10 should Liz Truss flounder before the next election.

One Tory insider said: “Darn right he wants another go. They are waiting to see how Liz does but if she doesn’t do their bidding, Boris will be dusted off.”

Speaking as he departed No 10, Johnson said: “Like Cincinnatus I am returning to my plough” – a line he previously used as London mayor when asked about his prime ministerial ambitions.

Johnson is likely to have known the remark would raise eyebrows. Cincinnatus returned to Rome when called upon to be appointed temporary dictator.

The historian Mary Beard pointed out that Cincinnatus’s cause was against the common citizens, known as the plebeians. “He was in fact an enemy of the people,” she tweeted.

As mayor, Johnson used the comparison to raise the prospect of running for prime minister, saying: “If, like Cincinnatus, I were to be called from my plough, then obviously it would be wrong of me not to help out.”

Polling from Savanta ComRes found that 60% of Conservative voters saw Johnson as an asset to the party, though more than half of all voters said Johnson should not be able to return to frontline politics.

Over the coming months Johnson is expected to take up lucrative speaking and book deals, but one ally said he was wary of the reputational risks that had dogged former prime ministers such as Tony Blair and David Cameron, who took on well-paid roles in business and international affairs that drew them into embarrassing scandals.

Sources close to Johnson played down suggestions that he would plot damaging interventions akin to those of his predecessor Theresa May, but said he would work to keep the focus on two of his key pledges as prime minister – support for Ukraine and for levelling up.

Some friends have counselled against him plotting a return. A friend of Johnson’s said: “He’s delusional. He needs therapy if he thinks what the country needs right now is Boris back in No 10.”

Those hoping for a return of Johnson have been quietly disappointed by the lack of any significant uprising by the Tory membership. A grassroots petition attracted a lot of signatures but not enough from eligible members.

There appeared to be limited appetite among members to spoil their ballots in favour of Johnson, which was another grassroots campaign. Just 654 ballots were spoiled, only slightly more than the number in 2019.

Of those spoiled ballots, not all contained write-ins for Johnson, according to internal sources. “The grassroots clamour for a Boris return is a delusion,” one Conservative source said.

Johnson spent his final hour in No 10 having bacon sandwiches with his wife, Carrie, and some of his closest aides and MPs, including Nadine Dorries and Jacob Rees-Mogg, who brought his eldest son along. Some came with leaving presents for Johnson and asked for selfies.

The majority of Johnson’s aides have been told by Truss’s team that they will be leaving, including some who had expressed hopes of remaining, with one source saying there had been some anger and upset at the brutal nature of their departure.

Those leaving including Johnson’s director of communications, Guto Harri, his press secretary, Rosie Bate-Williams, and most of his policy unit and political team, including the former Lynton Crosby ally David Canzini who had been tipped to stay.

In his parting words, Johnson launched a final broadside about being forced out by the mass resignation of his ministers after a series of scandals. He said the “baton will be handed over” as his premiership had “unexpectedly turned out to be a relay race – they changed the rules halfway through”.

Harri posted a dig at the party for ousting Johnson. “It was far too brief. I saw an exceptional Prime Minister put in a massive shift, but the die – tragically – was cast,” he wrote on LinkedIn. “Seven months on the frontline was relentless, exhausting, a huge challenge intellectually, emotionally and even physically. At times, not least when the Conservative party showed its collective appetite for self-harm, it was brutal.”

In a message to Conservative MPs, Johnson said it was “time for politics to be over” and said they must back Truss and deliver for the country. “That is what the people of this country want, that’s what they need and that’s what they deserve.”

He ran though some of his government’s achievements, including the response to Covid-19, the vaccine rollout and the support for Ukraine against Russia’s invasion, as well as changes to social care and pledges of new nurses, police and new hospitals – promises that have regularly drawn criticism for inaccuracy.

Johnson said he would remain loyal and supportive to Truss after his departure. “Let me say that I am now like one of those booster rockets that has fulfilled its function and I will now be gently re-entering the atmosphere and splashing down invisibly in some remote and obscure corner of the Pacific,” he said. He said he would be offering the new government nothing but “the most fervent support”.

Johnson thanked staff and civil servants and departed with another warning to his party, referring to his dog and the No 10 cat. “If Dilyn and Larry can put behind them their occasional difficulties, then so can the Conservative party,” he said.