John Cleese has said that he “can hardly believe” the decision by GB News to platform former prime minister Boris Johnson. On Sunday the Fawlty Towers star will make his debut on the news channel with new show The Dinosaur Hour which sees Cleese, 84, interview a range of people from inside a 12th-century castle. On Saturday, a day before he is scheduled to appear on screen, Cleese reposted an image of Boris Johnson to X, formerly Twitter, and wrote that he could not believe GB News had hired a “serial liar”. “I can hardly believe that GB News will give this proven serial liar his own programme,” he wrote. Johnson is the latest Conservative politician to find a place at the broadcaster. In a video posted to social media on Friday, the former prime minister announced he would be giving his “unvarnished views” on the channel. In the video he said: “I am excited to say that I am shortly going to be joining you on GB News. “I’m going to be giving this remarkable new TV channel my unvarnished views on everything from Russia, China, the war in Ukraine, how we meet all those challenges, to the huge opportunities that lie ahead for us, why I believe our best days are yet to come. “And why on the whole the people of the world want to see more ‘global Britain’, not less.” Cleese’s 10-part series The Dinosaur Hour will air on Sunday at 9pm and a preview clip from the show has teased guests that include comedian and actor Stephen Fry, media personality Caitlyn Jenner and journalist Sir Trevor McDonald. Last year, after the announcement that Cleese would be joining the broadcaster, the comedian and actor spoke to journalist Amol Rajan on BBC Radio 4’s Today programme about his move. He said: “I met one or two of the people concerned and had dinner with them and I liked them very much. “And what they said was: ‘People say it’s the rightwing channel; it’s a free speech channel.’” Cleese is best known for Monty Python’s Flying Circus and for playing Basil Fawlty in the hit TV series Fawlty Towers. GB News and Boris Johnson have been approached for comment.