Downing Street probably hoped Dominic Cummings’ family would not provide any more headaches after the furore prompted by Boris Johnson’s adviser’s lockdown dash to his parents’ Durham farm this year. But, in a fresh blow to No 10, the top aide’s father-in-law has reportedly said Johnson will stand down as prime minister in six months. The claim – strenuously denied by Downing Street and, later, Johnson – was apparently delivered by Sir Humphry Wakefield to a visitor to the family’s 13th-century Grade I-listed Chillingham Castle, in Northumberland, last week. The 84-year-old baronet, father of Cummings’ wife, Mary, told visitor Anna Silverman Johnson was still struggling badly after having coronavirus and would step down in six months, according to a report in the Times. Wakefield, a lifelong horse rider, is said to have likened the virus to being gone in the fetlock, a horse’s joint. “If you put a horse back to work when it’s injured it will never recover,” he reportedly said. Asked during a visit to a shipyard in north Devon on Tuesday about the claim he would be standing down as prime minister, Johnson told a Devon Live reporter: “It’s absolute nonsense! I am feeling, if anything, far better as I’ve lost some weight. Not enough, but I have lost at least a stone and a half. “I feel much much better for having lost, by my standards, quite a lot of weight.” No 10 had earlier also dismissed the claim as “utter nonsense”. Wakefield could not be reached for comment. According to research released this month as part of the preliminary results into a study of the long-term effects of coronavirus, nearly three-quarters of a sample group of Covid-19 patients admitted to hospital had ongoing symptoms three months later. Johnson contracted coronavirus in March. The following month, after his condition deteriorated, he was admitted to St Thomas’ hospital in London where he spent a week, including three nights in intensive care, before being discharged. In a later interview, Johnson revealed that while he was in hospital, he worried he would not live to see his new son, Wilfred, who was born at the end of April after the prime minister left hospital. Johnson told the Sun: “Well, yes, of course. We’ve all got a lot to live for, a lot to do, and I won’t hide it from you, I was thinking about that, yes.” He added: “I was deeply frustrated that I couldn’t see the path to … do you know what I mean? I just couldn’t see the way out of the skip. But, yeah, I suppose there was some terrible, as I say, some natural buoyancy or refusal to give in or harbour negative thoughts. I never really thought that I wouldn’t come back from it. It was more frustration.” A joint investigation by the Guardian and the Mirror in May revealed that Cummings travelled 264 miles from London to Durham with his wife and child during lockdown, leading to calls for him to be sacked. Cummings later said he did not regret the trip, explaining during a press conference that he stayed in a cottage on his parents’ farm. In a now infamous excuse, he claimed a separate 30-mile trip to Barnard Castle on Easter Sunday was to test his eyesight to ensure he would be OK to drive back to London.