Dominic Cummings has published new revelations on his blog, claiming the prime minister was warned on multiple occasions about a party at No 10 during the first lockdown, where invitees were asked to “bring your own booze” to the garden. What does Cummings claim? The PM’s former chief adviser, now turned nemesis, was the first to reveal a party organised by Johnson’s principal private secretary, Martin Reynolds, during the first lockdown, when it was only permitted to socialise outdoors with one other person. Johnson has admitted he was at the gathering but claimed he believed it was a work event, which is what he told MPs in the House of Commons. Cummings now claims Johnson lied to the house – a serious charge – and that Reynolds was warned the event broke the rules by another senior official but took the PM’s guidance that it should go ahead. He also claims to have told the prime minister himself that the event was against the rules. “The events of 20 May alone, never mind the string of other events, mean the PM lied to parliament about parties,” Cummings wrote on Substack. Who else can corroborate Cummings’ claim? There are a number of senior officials who worked closely with Cummings and Johnson during that period in Downing Street who are known to have been unnerved by some of the antics in Downing Street. The Guardian has spoken to one official who claims to have raised concerns within the office, and multiple other newspapers and broadcast journalists have also been told concerns were raised – off the record. Cummings claims that his vocal concerns were witnessed by others. “Not only me but other eyewitnesses who discussed this at the time would swear under oath this is what happened.” Will anyone else go public? The track record is not great. Cummings had made similar claims before – including that other officials heard the “let the bodies pile high” remark made by the PM ahead of the second lockdown. Though this has been claimed by another source off the record, no one else has ever gone on record. Is there a written record of Cummings’ own interventions? Cummings claims to have told Reynolds in person that his invite broke the rules and that an email was sent by another very senior official. “This email will be seen by Sue Gray (unless there is a foolish cover-up which would also probably be a criminal offence),” Cummings wrote. Cummings then claimed to have told the prime minister in person that the invite broke the rules. “Amid discussion over the future of the cabinet secretary and PPS himself, which had been going on for days, I said to the PM something like: Martin’s invited the building to a drinks party, this is what I’m talking about, you’ve got to grip this madhouse,” he wrote. “The PM waved it aside.” Why does Cummings claim that 15 May was a work event and 20 May was not? Cummings himself was pictured with a glass of wine next to Reynolds and Johnson, as well as Johnson’s wife Carrie, in the Downing Street garden on 15 May in a picture leaked to the Guardian. Cummings claims that was, indeed, a work event. He said that officials regularly had meetings outside to ensure good ventilation. “The meeting ended roughly 6-6.30. The PM and I continued talking as it broke up.” He said either the PM or Reynolds had brought out a bottle of wine but that they had continued “chatting about Covid, about domestic priorities, and about how to sort out the Cabinet Office, which had totally collapsed.” Cummings, a fierce critic of Carrie Johnson, said she was permitted to join them. “Nobody has been as critical of her as I have for her influence on the PM and No 10 but it is an unarguable legal fact that she was allowed by ‘the rules’ to be in the garden in her own home.” Can Sue Gray interview Cummings as part of her inquiry? Yes, Sue Gray is permitted to interview Cummings who has said he will answer questions. It is not yet clear whether she will decide to do so but his evidence could lead to a major expansion of the investigation – and delay its publication. Is Cummings to be trusted? Cummings himself was infamously found to have breached the first lockdown, though he claimed he was following guidance, when he drove his family to Durham while his wife was sick, and later visited Barnard Castle claiming to have been testing his eyesight for the drive back to London. His excuses, made in a Downing Street rose garden press conference, stretched the limits of credibility. He has since emphasised that his main reason for leaving London were threats he had been receiving and that he believed his family were at risk. There were other times too when Cummings has overpromised and underdelivered – including a promise to provide evidence that former health secretary Matt Hancock had lied, which he has not published.