It sounds like something out of a cold case thriller: an undercover police officer poses as a hardened criminal and befriends a suspected murderer. The suspect comes to regard the officer as his best friend and eventually confesses. During a trial at Bristol crown court, a jury was given a rare insight into a true-life relationship between an undercover police officer who went by the fake name Paddy O’Hara and Darren Osment, who was suspected of killing his former partner Claire Holland. After spending hundreds of hours together, in pool rooms, on road trips, during night-time walks, Osment opened up and gave Holland’s family at least partial answers to the mystery of her disappearance aged 32 in June 2012. The genesis for the operation came in 2019 when Osment, drunk and racked with guilt, phoned police and claimed he had killed Holland. “I just want the monkey off my back,” he said. After he sobered up, he claimed it had been the drink talking and denied any involvement. Detectives began to reinvestigate Holland’s disappearance. Though the mother of four had at times led a chaotic life, she was doing well when she went missing, excited to move into a new flat and getting on well with her family. When they looked into Osment’s life, they found he was a domestic abuser and a misogynist with a furious temper. They also discovered that over the years he had hinted to friends and girlfriends that he had been involved in Holland’s disappearance. But the passage of time, the lack of any other physical evidence and, crucially, the absence of Holland’s body meant detectives did not have enough to charge Osment. Officers asked permission of the chief constable and the Investigatory Powers Commissioner’s Office, which oversees the use of covert operations, to send in an undercover officer. They took advice from well-known criminal psychologists and designed a cover story for O’Hara. Towards the end of 2020, he moved into a flat in Patchway, just north of Bristol, about 300 metres from Osment’s home, and one day struck up a conversation. Osment mentioned he was struggling to find a job and O’Hara asked him if he wanted to do casual work for him shifting boxes of counterfeit and stolen clothing around a lock-up. Their work relationship soon turned into a friendship, with Osment frequently going to O’Hara’s flat to watch football and they would play pool sometimes for 10 hours a day. The officer would drive Osment to hospital appointments and take him to meetings with customers to sell cannabis. To win Osment’s trust, pieces of “theatre” had been plotted to convince him that O’Hara was a criminal. O’Hara got Osment to act as a lookout while he pretended to hide cash and silver medallions in woods. Another undercover officer, referred to as Mike, posed as a criminal contact of O’Hara’s while a third – Neil – was presented as a “fixer” of problems. Gradually, O’Hara pretended to open up to secrets in his past. On one occasion, he showed Osment a fake newspaper clipping relating to a killing in Belfast in 1985 and implied he was involved in it. Every word was recorded, more than 1,200 hours in all. O’Hara had been instructed to ask “open questions”, not ones that went to the heart of the investigation. He started very carefully. On one day in May 2021, for example, O’Hara vaguely suggested he could help Osment escape if he needed to. “South of Spain is nice,” he told Osment. The following month O’Hara asked Osment what he thought of women having equal billing in sport. The subject clearly riled Osment and he admitted he once threw Holland downstairs. O’Hara had to pretend to be as brutal as Osment. After a row Osment had with someone over a mobile phone, O’Hara suggested he “drop kick his fucking head over a field”. The officer was frequently torn between the need to protect the public from Osment’s daily bouts of aggression and the imperative not to blow his cover. By October 2021 Osment clearly trusted O’Hara, telling him: “If I was getting married next week, you’d be my best man.” At this point he admitted: “She [Holland] ain’t gonna be seeing the light of day again, don’t worry about that.” They took night-time walks next to the Severn estuary and Osment hinted Holland had been dumped in the water. By the following March, Osment knew the police were on to him, while never knowing how close one officer was to him: “They’re putting the puzzle together but they haven’t got all the bits,” he told O’Hara. In April 2022 he felt close enough to O’Hara to tell him about the dreams he had about Holland. “What does her face look like when you see it?” O’Hara asked. “Black black eyes,” Osment replied. On 15 June 2022 a breakthrough came after O’Hara urged Osment to open up for his own sake: “Daz, this is the problem mate … you’ve never really talked to me … I think the fact you’ve been carrying this for so fucking long mate, I think it’s tearing you apart … I think I need to protect you … I know you fucking killed the bitch but … you’ve never told me about, like, any of the details.” Osment told O’Hara: “Mate, I trust you like a fucking brother,” and told him he had arranged to meet Holland at the pub where he worked as a chef in the Clifton area of Bristol. “It was an easy fucking lure,” he said. “There’s not CCTV there.” He said he used his “knife skills” and he demonstrated on his own torso how he had cut Holland’s body. He mentioned the body being weighted and that it “wasn’t going to come floating up”. He had burnt the clothes he was wearing and got rid of a knife by putting it in someone else’s equipment box. “Do you feel a little bit better just talking to me?” O’Hara asked. “Sick but I feel another weight’s come off my shoulders a bit,” Osment replied. O’Hara told him: “You’re sharing the burden mate … it’s you and me against everything.” The undercover officer vanished from Osment’s life as quietly as he had appeared and in August 2022 the suspect was arrested and charged. During legal argument, Osment’s defence argued the police tactics had been unfair and that he had been coaxed into a false confession. Under UK law, a confession is disregarded in court if it is deemed that police obtained it through oppressive pressure or overbearing behaviour. They also complained that Osment, an alcoholic, had been bought drinks to loosen his tongue. But O’Hara’s evidence was allowed to go before the jury. Speaking after Osment’s conviction, Det Supt Darren Hannant, the senior investigating officer, said unless the killer told them, they might never know what exactly happened to Holland. He said: “I believe he killed her himself. He met somewhere near the pub. I think he killed her in anger. He could have had some assistance in disposing of her body or could have done it himself.” Under the so-called Helen’s law, it is very hard for killers to win parole if they refuse to reveal the location of their victim’s body. Meanwhile, O’Hara has gone. “I don’t know anything about him as an individual,” said Hannant. “None of my investigative team know him or have ever met him – only the covert people know him. That’s how it is for his own welfare.” He said O’Hara had been brave and patient and he was sure the covert operation was the only way to get justice for Holland. “I wonder how we could have done this any other way, I’m not sure we could.”