As a veteran News of the World reporter, Stuart Collier spent much of his Fleet Street career exposing villains. But the only criminal he investigated who prompted a threat to him and his family’s safety was Boris Johnson’s close friend Darius Guppy. Guppy’s secretly recorded plot in 1990 to have Johnson – then a young Daily Telegraph Brussels correspondent – supply him with Collier’s address so he could send over heavies to beat him up came to nothing. Almost 30 years later, with Johnson’s journey to Downing Street nearly complete, Collier is still waiting for an apology from the Conservative MP for his involvement in the “Guppygate” scandal. Guppy ended up being jailed for staging a fake £1.8m jewellery heist – thought to be the subject of Collier’s inquiries. Some years later, the 69-year-old journalist left the NoW for a quieter existence in the Oxfordshire countryside, where he worked as a postman and Tesco delivery driver before retirement. Collier has kept a mountain of cuttings from his career, which also included a 10-year stint at the Daily Mail, during which he covered Princess Diana’s wedding to Prince Charles. Though he has long been out of journalism, his enthusiasm grows as he recalls stories of his early days on Fleet Street. Sitting in the home he shares with his 64-year-old wife, Jennifer – a former nurse who now works for a charity – one episode during his career still rankles. “I do think he [Boris Johnson] should definitely apologise,” Collier said. “I’ve been more incensed reading over the stories about him in the newspaper and it strikes me as being scandalous he could have possibly been in league with Darius Guppy in a plot to get me beat up. “Fortunately it never happened, but for a possible future leader of the Tory party to be involved in that way is absolutely dreadful, in my opinion.” Asked about Johnson’s explanation that he was acting out of loyalty to an old friend, Collier said: “He might have gone to Eton with Guppy, but loyalty shouldn’t really extend to plotting to have a journalist beaten up. I’m just amazed that he acted in this way, that he didn’t have the gumption not to get involved with someone like Guppy. “He went quite a way along the line of plotting to get me beat up. He didn’t dismiss it from what I gather … From reading the transcript, he was well prepared to help Guppy find my address and for Guppy to then get me assaulted.” On the taped call, Guppy tells Johnson he wants to scare Collier by getting heavies to give him “a couple of black eyes” and a “cracked rib”. Appearing to indicate he is happy to help supply Collier’s address, Johnson is heard saying at the end of the call: “OK, Darry, I said I’ll do it. I’ll do it, don’t worry.” After the tape emerged, Collier said, he was interviewed by a police officer. “By that time I knew that there was a plot to find me,” Collier recalled. “But I didn’t want to get involved in pressing any charges. I just really wanted to get on with my life. Fortunately, nothing came of Guppy’s threats or Boris’s involvement.” He does not regret his decision not to take it further with police at the time and has no plans to now. “I was just keen to get on with my job as a NoW reporter,” he explained. “I had warned my wife to be aware of the situation but, over the years, I’ve thought that Johnson could at least have made some approach to apologise, especially as it became more likely he might be leading the Tory party. I’m amazed that he’s entered this leadership race with this sort of skeleton in his cupboard.” Collier added: “I would like it to become public knowledge again … It’s just basic honesty. Everyone has made mistakes. If he views this as a mistake then he should say so.” He recalled how his wife was at home with their young son, Ross, when he learned of the plot to have him assaulted and warned her to be careful opening the door. “My wife still talks about Johnson,” he said. Collier, who left the NoW in the late 1990s, long before the hacking scandal exposed by the Guardian culminated in the newspaper’s closure in 2011, said: “Naturally, as a NoW reporter, I did a lot of stories where people wanted revenge on me. I reported those stories properly and honestly because they were criminals, but there was always a danger that they might find me and punish me in some way.” While he only learned of the call between Johnson and Guppy much later, the discovery was sufficiently unnerving to make him worry for his family’s safety. “My wife was genuinely concerned and I warned her to be careful about who she opened the door to. We had a young son, Ross, at the time, so she was a mother at home. Johnson did cause me some concern and I did genuinely think that Guppy was a real threat to my safety.” Collier said anyone reading the transcript of Guppy’s call with Johnson would realise the future politician took the request seriously and was “prepared to do whatever he could to help his old school pal”, adding: “This wasn’t just a joking matter. He was going to help Guppy all he could.” Guppy later wrote a piece for the Spectator in which he said his only regret over the scandal was that he “didn’t finish the job”. Collier said: “I’m just thankful now that years have passed and Guppy is away [in South Africa].” For now, Collier is resigned to Johnson becoming the next prime minister, but he has a message for him. “I just don’t think you’re fit to be prime minister. At the very least, come clean on all your skeletons in the closet. I’m sure this is just one of them,” he said. Johnson’s campaign did not respond to a request for comment.