BBC staff openly smoked weed at the broadcaster’s headquarters and visiting pop stars would light up joints in the corridors, it was claimed.

In an interview for a TV documentary, former Play School presenter Johnny Ball said that fellow presenters Rick Jones and Lionel Morton “got stoned on the biggest joint you’ve ever seen – in the studio”.

No wonder children’s TV presenters always seem unnaturally happy.

Ball, now 73, added that, as scenes for the programme were filmed, “They were absolutely stoned out of their minds.”

He said that he wasn’t stoned himself because he “couldn’t work with it”.

Meanwhile, presenter Joan Bakewell said of the pop and rock stars that frequently visited the BBC HQ: “Of course they smoked and they didn’t smoke ordinary cigarettes.”

Completing the trio with drugs and rock n’ roll, other former BBC employees said that staff often had sex in their dressing rooms.

Former Doctor Who actress Katy Manning said: “People were bonking all over the BBC. Everybody was doing it on the premises.”

The revelations are made in BBC Four’s Tales Of Television Centre, screening on May 17.