Norfolk man Alan Smith and "Fake Sheikh" reporter Mazher Mahmood have been found guilty of conspiring to pervert the course of justice following a trial at the Old Bailey.
The former undercover News of the World reporter, 53, and Smith, 67, conspired to suppress evidence in the collapsed drugs trial of N-Dubz singer Tulisa Contostavlos.
The singer had been accused of arranging for Mahmood to be sold £800 of cocaine by one of her contacts following an elaborate sting for the Sun on Sunday in May 2013.
During a meeting at the Metropolitan Hotel in London, Mahmood pretended to be a film producer and plied Miss Contostavlos with alcohol as they discussed an acting role alongside Hollywood star Leonardo DiCaprio.
As Smith, who is from Dereham, drove the former X Factor judge to her Hertfordshire home, she allegedly discussed a family member who had a drugs problem.
When he was interviewed by police about the journey over a year later, Smith recalled the conversation.
However, a day later, after speaking to Mahmood and emailing his draft statement, the singer's anti-drugs comments were removed, the court heard.