Mr Canzini is a former director of campaigning at the Conservative Party, who has spent more than two decades in Tory politics of some description.

He keeps a low profile. His Twitter name is “DCGrumpy”, with a photograph of Darth Vader wearing a poppy and an account biography which reads: “Who cares who or what I am?”

Mr Canzini has deep roots in the party. In 2019, he advised Eurosceptic Tory MPs on the “Chuck Chequers” campaign, which lobbied against Theresa May’s Brexit deal blueprint.

He was also tasked with revitalising Change Britain, a pro-Brexit pressure group set up after the referendum, and giving Mr Johnson a personal platform.

Mr Canzini’s long-term links to politicians – he worked on Tory MP turned Johnson-rebel David Davis’s 2005 leadership campaign – is seen as a critical advantage which could help quell the rebellion.

‘He just gets it’

“He’s got really good relationships with MPs,” one source who has worked alongside him said. “He knows how campaigns work. He knows how politics works. He just gets it.”

Mr Canzini’s potential move into Downing Street was mooted late last year. It did not come to fruition then, but is understood to be under serious consideration now in Number 10.

His long association with Sir Lynton, the Australian election guru who helped Mr Johnson secure his London mayoral victories and the 2019 Tory leadership, may be a factor.

Ms Romeo currently is the most senior civil servant in the Justice Department, meaning working with Dominic Raab, the Deputy Prime Minister who took on the brief in September.

Before that she was the permanent secretary at the International Trade Department and the British Consul General in New York – one of the plum UK diplomatic posts in America.

She was in the running to be the Cabinet Secretary – the head of the UK civil service – last year but lost out to Simon Case, who became the youngest person ever to get the role.

But the fact that she made the final list of contenders shows how highly she is regarded in Mr Johnson’s Downing Street – a good omen for the possibility of a new position there.

Ms Romeo was photographed entering Downing Street earlier in the month, triggering speculation among Justice Department officials who were unaware of a scheduled meeting.

One possibility would be Ms Romeo taking up the role of Number 10 permanent secretary, which was briefly created for Mr Case last year but currently does not exist.

Final decisions are yet to be taken on the new staffing, with changes unlikely to be confirmed and announced until Ms Gray’s report is published.