Downing Street is braced for more explosive revelations from the Prime Minister’s former chief advisor Dominic Cummings as he makes a much-anticipated appearance before MPs on Wednesday. Mr Cummings has been vocal in his condemnation of Boris Johnson, Health Secretary Matt Hancock, and others since leaving Government after a behind-the-scenes power struggle in November. Ahead of giving evidence to the Commons Health and Social Care and Science and Technology Committees, Mr Cummings set out his criticisms of the Government’s approach to the pandemic in a thread of messages on Twitter, claiming the original response to the coronavirus outbreak was to pursue a strategy of “herd immunity”. Series of tweets teases revelations In a series of explosive tweets, he said the policy, to build up resistance in the population by allowing some spread of the disease, was only dropped in March last year after a warning it would lead to a “catastrophe”. Multiple Cabinet ministers have denied this was the case, and the Prime Minister’s official spokesman told reporters: “Herd immunity from infection has never been government policy.” The spokesman added: “At all times we have been guided by the data and the latest evidence we have had through this coronavirus pandemic.” He added: “As our understanding of the virus progressed, more data became available, it was clear that a national lockdown was needed to suppress the curve, save lives and protect the NHS from being overwhelmed.” When he last appeared before MPs in March, Mr Cummings said the Department of Health and Social Care was reduced to a “smoking ruin” by the coronavirus pandemic. Ahead of Wednesday’s session, ITV’s Robert Peston reported on Tuesday that Mr Cummings will allege the PM said “Covid is only killing 80-year-olds” in a bid to delay the autumn lockdown. Downing Street did not deny Mr Johnson made the remarks, but when asked about the report said: “There is a huge task for this Government to get on with. “We are entirely focused on recovering from the pandemic, moving through the road map and distributing vaccines while delivering on the public’s priorities. “Throughout this pandemic, the Government’s priority has been to save lives, protect the NHS and support people’s jobs and livelihoods across the United Kingdom.” Labour deputy leader Angela Rayner said the alleged comments were “utterly disgraceful”. Covid plan ‘turned out to be part disaster, part non-existent’ Mr Cummings has also hit out at various parts of the Government’s response, despite being employed by No 10 for a large part of the pandemic. He dubbed the policy at the UK’s borders a “joke” and said: “The Covid plan was supposed to be ‘world class’ but turned out to be part disaster, part non-existent.” In his series of tweets earlier this week he slammed alleged “secrecy” in Government plans and said mass testing should have been developed much earlier. And he was insistent herd immunity – to build up resistance in the population by allowing some spread of the disease – was the Government’s original plan before ministers were told this would lead to “catastrophe”. No 10 also faced questions after a Sunday Times report suggested officials fear Mr Cummings will use his appearance before MPs to accuse Mr Johnson of missing key meetings on the crisis because he was working on a biography of Shakespeare, because he needed the money to fund his divorce from Marina Wheeler, his second wife. Asked if the Prime Minister had spent time on the book, his official spokesman said: “No, not that I’m aware of.” The Prime Minister has been “ensuring the public are kept as protected as possible during this global pandemic”, the spokesman added. The relationship between Mr Johnson and Mr Cummings is thought to have soured after a briefing war over the so-called “chatty rat” leak of plans for a second lockdown. No 10 accused Mr Cummings of a series of damaging leaks, including text message exchanges between Mr Johnson and the entrepreneur Sir James Dyson. But the claim led Mr Cummings to post an incendiary blog post with a number of damaging allegations against the PM. Mr Cummings’ evidence session takes place a day after the anniversary of his sensational press conference in No 10’s rose garden, where he sought to justify breaking lockdown rules with a trip to County Durham and Barnard Castle in late March 2020.