Downing Street has been urged to provide proof that Dominic Cummings did not make a second trip to Durham during lockdown amid claims that police failed to properly investigate alleged sightings of the prime minister’s chief aide. Two of four people who claim to have seen Cummings on what would have been a second visit to the north-east of England have complained to the police watchdog, accusing the Durham force of not fully probing their claims. Cummings has consistently denied returning to Durham on 19 April, days after he came back to London from a trip that was subsequently exposed in a joint investigation by the Guardian and the Daily Mirror. The prime minister’s chief adviser has said that phone data and potentially CCTV would prove he was in London – and the Guardian has been told of one sighting of him on Hampstead Heath that afternoon. However, neither he nor Downing Street has gone public with the evidence they say they have – and which Boris Johnson says he has seen – and pressure is mounting again for full transparency to answer lingering questions about his movements. Cummings’ initial trip to Durham caused widespread uproar and is cited as one of the chief reasons for the public losing faith in the government’s handling of the crisis. Clare Edwards, a nurse practitioner, and her husband, Dave, say they saw a man they believe to have been Cummings on 19 April just after 11am in Houghall woods on the edge of Durham. On 25 May they gave statements to police about the alleged sighting, just as Cummings was giving a press conference in Downing Street denying a claim by another witness that he was seen admiring bluebells with his wife in the same woods on 19 April, at about 8.30am. Since then, a fourth witness has alleged they saw the No 10 aide and a companion in between the woods and the home of Cummings’ parents that day, between 11.15am and 11.30am. A further witness told the Guardian that they saw Cummings back in north London, on Hampstead Heath, later the same afternoon. Durham police found “insufficient evidence” that Cummings was in Durham on 19 April. Following that assessment, Clare and Dave Edwards, both 59, made a subject access request under the Data Protection Act, asking the force to show them all the personal information it had about them as a result of their complaint, which they hoped might reveal how it was followed up. Most of the police correspondence about their original complaints was redacted and labelled “official – sensitive”. All pre-dated the statements given to police, which Dave Edwards suggests means the police did nothing more with those statements. Edwards said he believed the results, returned last week, suggested that their testimony was not taken seriously. On Wednesday the couple complained to the Independent Office for Police Conduct. They said: “Given the high-profile nature of this issue, it is inconceivable that this matter has not been followed up thoroughly. We have no personal issue with Mr Cummings or his family, but we do feel that Durham police’s handling of our complaint is below the standard we would expect from our local constabulary.” The Edwardses asked whether officers checked automatic number recognition cameras for the movements of Cummings’ car that weekend. This information would not typically be revealed under a subject access request, and the force did not answer. Dave Edwards, who works for a manufacturing company that supplied some of the Nightingale hospitals, remains convinced that he saw Cummings among a group of five adults and a child. “He was the dead image of Dominic Cummings. He was standing over a small child on a bike. As I got through the clearing, I said to my wife: ‘Did you see Dominic Cummings there?’ “He was identical to the TV footage: dark beanie hat, dark-rimmed glasses. If it was mistaken identity, the police could have ruled that out. If Cummings had the evidence, it would be very easy for him to say: ‘Here I am in Costa coffee in London at 10am on 19 April,’ or whatever, ‘so I couldn’t have been in Houghall woods.’ “I’m not politically motivated, I have nothing against Cummings. But we think what we saw was important given the circumstances of the lockdown, and we feel that our complaint has been airbrushed.” Clare Edwards said: “I’m certainly sure that it was Dominic Cummings.” In her statement to officers, she said she saw a man she thought to be Cummings just after 11.01am on 19 April. She said she was able to be precise after finding a timestamped geolocated photograph she took of the woods moments before seeing the man. The couple remember the date because they had a Zoom party and quiz for their son’s birthday the day before as they were not allowed to meet due to the lockdown restrictions. Clare Edwards also called on Cummings to release evidence proving he was in London at the time. A fourth witness, who does not want to be named, is convinced that they saw Cummings and a companion between 11.15am and 11.30am that day, between Houghall woods and Cummings’ father’s property. They made a digital note of the sighting, including location data, which was shared with friends at the time. That note has been seen by the Guardian and Daily Mirror. The witness said: “I do follow politics, so I know what people look like.” Asked whether they were sure it was Cummings, they said: “We know his parents do live locally, so we have recognised them before in the local area. I would recognise him again. At first I could not quite believe that I had seen him. I thought: ‘Why would he be up here?’ But I posted about it on the day. I was sure about it at the time.” A No 10 spokesman said: “Durham constabulary have made clear they are not taking any further action against Mr Cummings and that by locating himself at his father’s premises he did not breach the regulations. “The prime minister has said he believes Mr Cummings behaved reasonably and he considers the matter closed.” No 10 did not comment on specific allegations that Cummings was in Durham on 19 April. Cummings has defended driving to his parents’ farm from London on 27 March after fearing that he and his wife were falling ill with coronavirus, to seek potential childcare for their four-year-old son. They made a 60-mile round trip to Barnard Castle on 12 April – Cummings said to test his eyesight – and drove back to London the following day. At his press conference in the Downing Street rose garden in May, he said it was false to claim he returned to Durham again after coming back to London on 13 April. He said: “There is a particular report that I returned there on the 19 April. Photos and data on my phone prove this to be false. And local CCTV, if it exists, would also prove that I’m telling the truth that I was in London on that day. I was not in Durham.” Cummings said witnesses who claimed they saw him in the bluebell wood on 19 April were mistaken. He said he had walked in woodland during his self-isolation period, but only on his father’s property. At the end of May, the prime minister was challenged by the Commons liaison committee about whether he had seen the evidence. After dodging the question three times, he said he had, but refused MPs’ requests to publish the evidence or pass it to the cabinet secretary for independent scrutiny. The Guardian asked Downing Street to provide the data to rule out a case of mistaken identity on 19 April, but it declined. A Durham police spokesman said: “As outlined in our statement of 28 May, Durham constabulary carried out an investigation into this matter led by a senior detective and found insufficient evidence to support the allegation.” • Additional reporting by Duncan Campbell