LONDON, May 3 (UPI) -- Stars of BBC programs from the 1960s and '70s told a documentary how the station was formerly a hotbed of drugs and sex, even on children's shows. Johnny Ball, a former star of children's show "Play School," said colleagues Rick Jones and Lionel Morton once smoked "the biggest joint you've ever seen" right before going on TV as shepherds in a nativity scene, The Sun reported Thursday. "They were absolutely stoned out of their minds," he said. Ball and other former BBC stars spoke of the drugs and sex at the station in previous decades while being interviewed for documentary "Tales Of Television Centre," which is set to premiere May 17 on BBC Four. Katy Manning, who played Jo Grant on "Doctor Who" from 1971 to 1973, said sex was common in the studio. "People were bonking all over the BBC. Everybody was doing it on the premises," she said.