The power of Sue Gray’s ‘update’ of her investigation into parties at 10 Downing Street and the Cabinet Office is as much in what it doesn’t say, as what it does. She identifies a staggering 12 gatherings – alleged rule-breaking parties – that took place over 11 months between May 2020 and April 2021 that may have breached the criminal law, the Covid regulations in force at the time.

The resonant point about these gatherings is Sue Gray feels she cannot tell us anything about them, because they are being investigated by the Met police. She does not want to prejudice their inquiries. But the sheer number of potential criminal events will be seen by many as evidence of systematic abuse and flouting of Covid rules by senior members of the government who wrote those very rules. It reinforces the impression of rot in an institution supposed to be beyond reproach.

One of these gatherings took place in the Prime Minister’s own home, the Downing Street flat, on 13 November 2020. It was allegedly to celebrate the eviction from government of Dominic Cummings, who was then the Prime Minister’s chief aide and is now his arch tormentor.

One of the few conclusions Gray allows herself to make reverberates with suppressed fury, from someone who has devoted her life to serving assorted governments:

‘At least some of the gatherings in question represent a serious failure to observe not just the high standards expected of those working at the heart of government but also of the standards expected of the entire British population at the time.’

She criticises ‘the excessive consumption of alcohol’ in Downing Street; a culture that made it difficult for whistleblowers ‘to challenge poor conduct where they witness it’; and ‘leadership structures’ that are ‘fragmented’ with ‘blurred lines of responsibility’.

Her most important finding, however, is that ‘there were failures of leadership and judgment by different parts of No. 10 and the Cabinet Office at different times’.

This is problematic for a significant number of civil servants, including the cabinet secretary, Simon Case, the Prime Minister’s principal private secretary, Martin Reynolds, and assorted more junior officials. What is unclear is whether this ‘failure of leadership’ judgement will be lethal for the PM. He will try to paint himself as the victim of an incompetent, inefficient and rotten Downing Street system that he inherited. He will pledge to reform it and clean it up.

But if the police find, for example, that he should have known that the garden party on 20 May 2020 was a rule-breaking party, or that he should have run away from his birthday celebration on 19 June 2020, or that the event in his flat on 13 November broke the law, well then he could not pass the buck to colleagues.

If fined for all or any of those events, the fault would be firmly his. And under the ministerial code, which demands the highest standards of probity from all ministers, he would be obliged to resign. The censorship of Sue Gray’s report has not let the Prime Minister off the hook. It is now for the Met police to determine whether he can remain in 10 Downing Street.