The Metropolitan police has refused to help clarify whether Dominic Cummings made a second trip to Durham during lockdown at the height of the coronavirus pandemic. Deputy commissioner Sir Stephen House said he understood “the passion” the behaviour of Boris Johnson’s chief adviser provoked, but he insisted the Met was sticking to its decision not to retrospectively investigate breaches of the Covid regulations. Speaking to the London assembly, House suggested the Met did not have the resources to investigate whether Cummings left London for an alleged second trip to Durham on the weekend of 18-19 April. In May, Cummings admitted making the first trip at the end of March and a visit to Barnard Castle on 12 April, his wife’s birthday, as revealed by the Guardian and Daily Mirror. But he denied he was in Durham on 19 April, despite the testimony of a witness who said they saw him admiring bluebells that morning in Houghall woods on the outskirts of the city. Since then, three other witnesses, including two who complained to the police, said they also saw someone they believed to be Cummings on the morning of 19 April in the same area. In his Downing Street rose garden statement in May, Cummings said he had phone data to prove he was in London that day, but he has repeatedly refused to produce the evidence. Johnson told MPs he had seen this evidence but refused to submit it for independent scrutiny. Unmesh Desai, the Labour chair of the London assembly’s police and crime committee, urged House to help clear up the matter “in the interests of transparency”. He said: “The prime minister said that they had looked at the evidence [and] accepted that he was not there. There are four witnesses who said very clearly that they saw Mr Cummings in Durham. Shouldn’t the Met investigate where he was on 19 April?” House replied: “I understand the passion involved in it. But the Met is not investigating Covid breaches retrospectively.” In May, Durham police found Cummings may have breached health protection regulations by travelling to Barnard Castle, but they concluded there was “insufficient evidence” that he was in Durham on 19 April. This prompted a complaint to the Independent Office for Police Conduct from Dave and Clare Edwards, who gave statements to the force claiming they saw him that morning. Desai suggested that as Durham police’s investigation may have been “compromised”, the Met could intervene to help settle the matter. He also said the disputed second trip should be a matter for the Met because it involved an allegation that he left London. But House rejected the request. He added: “We have spent a lot of this meeting talking about police resources stretched in relation to rape, public order and antisocial behaviour. We have to take some decisions, and that’s one of the ones we’ve taken.” Desai replied: “If people in [a senior] position will not set some standards then clearly the public will say, ‘Why should we then be subjected to the same restrictions?.’” London’s deputy mayor for crime and policing, Sophie Linden, said she could not instruct the Met to investigate. She said: “Politicians do not intervene or interfere in operational decision-making about who or who isn’t investigated.” But she added: “I think it’s incredibly important that everybody complies [with the Covid regulations]. When high-profile people blatantly flout the rules, it is incredibly damaging, and we saw that for the case that you’re referring to.”