The prime minister had been telling colleagues for weeks that he believed he would receive no further fines for breaching Covid rules, but many saw it as little more than typical Johnsonian bluster.

When it emerged on Thursday that he was correct – despite attending several of the dozen booze-fuelled gatherings held on his watch – one exasperated backbencher said simply: “No words.”

With Johnson reassured by the Metropolitan police that they would take no further action, his team are now close to getting the closure they have long hoped for. It appears for the moment that “Operation Save Big Dog”, as he reportedly called the effort to protect him, has succeeded.

Several senior figures were sacrificed over the scandal, including Johnson’s director of communications, Jack Doyle, and chief of staff, Dan Rosenfield – as well as his press secretary, Allegra Stratton, who resigned after being caught on film joking about a “cheese and wine” gathering she didn’t even attend.

The prime minister will give his own account in a public statement next week, no doubt adopting a similar apologetic tone to that seen in previous Partygate revelations, though it rarely appears to last much beyond his moment at the dispatch box.

Conveniently for No 10, the waters have been nicely muddied by the fact that the clean-living Rishi Sunak also received a fixed-penalty notice (FPN) for the one event Johnson was fined for – and that the Labour leader, Keir Starmer, is now being investigated by Durham constabulary over an alleged lockdown breach.

Of course, Johnson must still survive the scrutiny of Sue Gray, the senior civil servant whose full report into the party culture in locked-down Downing Street is now expected next week.

Gray’s truncated report, published in January, already highlighted what she called “failures of leadership and judgment by different parts of No 10 and the Cabinet Office at different times”, though she declined to specify individual names.

Johnson deliberately chose to interpret it at the time not as an indictment of his behaviour, but rather a plea for a shake-up in the management structures within No 10. Ministers such as Oliver Dowden reinforced that reading, claiming the prime minister was tackling the rotten culture that had developed in Downing Street.

But former insiders insist Johnson was absolutely central to the boozy culture that developed among his team, praising them for letting off steam and sometimes pouring drinks himself.

But senior civil servants were also culpable, and the balance of fines – with just one falling to the prime minister, 125 to others – will strengthen Johnson’s argument that he wasn’t the driving force behind many of the events, despite being the most senior person in the building.

Gray’s final report is expected to set out the details of what took place at each of the gatherings she investigated. Much of that information is already in the public domain but seeing it in black and white may still be shocking.

The question for backbench MPs will be to what extent they choose to hold the prime minister responsible for what took place. Many have remained carefully on the fence, citing the importance of allowing the Met and Gray investigations to take their course. They will now have to decide whether they can defend him in public.

Johnson also faces a privileges committee investigation in the weeks ahead that will examine whether he misled parliament by claiming all guidance was followed in No 10 – a misdemeanour that according to the ministerial code should result in resignation.

There are more moments of danger ahead, too, including two crucial byelections on 23 June, in Wakefield and Tiverton – which Labour and the Liberal Democrats respectively are optimistic about winning – and the bleak outlook for living standards, with Sunak and Johnson under intense pressure to do more to help.

Even if MPs conclude that receiving just a single FPN helps to airbrush out Johnson’s role in Partygate, the public may decide otherwise.

“The fact remains that he’s still been fined, and this doesn’t erode that or take that away, so in terms of the seriousness of the situation I don’t think it changes anything,” said the pollster James Johnson, of JL Partners. “It stops a bad situation getting worse; but the public made up their mind a long time ago.”