Wiki: "During a telephone call in 1990, Guppy asked Boris Johnson (then a journalist at The Telegraph) to provide the home address of News of the World journalist Stuart Collier. Collier had been making enquiries into Guppy's background, and in response, Guppy wanted to send someone to physically assault Collier. Johnson never discovered the reporter's address, and the attack never took place, but a tape of the conversation was leaked to the press in June 1995."

And on the Guardian website (article by Simon Murphy, 14 July 2019, "A couple of black eyes..." Note the existence of a thoroughly incriminating transcript of a phone call between Guppy and Johnson, Nigel.