Robert Downey Jr. sat for an interview to promote "The Avengers: Age of Ultron" ... but when the reporter changed topics to Downey's distant past, the actor walked out, telling the guy he didn't sign up for a Diane Sawyer sit-down.
Downey was talking all things Avengers with Channel 4 News in London Wednesday to promote the release of his new flick and he handled things like a hero until the interviewer -- Krishnan Guru-Murthy -- brought up prison, politics and family.
Downey cautions the guy, but Guru-Murthy was done talkin' cinema. Downey eventually removes the mic and walks out, but not before telling the guy he was was "a little Diane Sawyer-y."
