In the first of a three-part series, creators Dick Clement and Ian La Frenais, now in their 70s but still pitching ideas in Hollywood (“It’s Spielberg: tell him to go away!”) reveal the unlikely origins of and initial fears for one of our finest ever sitcoms. One fab sequence sees the pair dissect their favourite scene, chuckling along with every familiar line. Later, über-fan Keith Allen drives a police van around Porridge locations, while we hear rare Barker recordings intended for real prison inmates. Eric Idle points out the roundedness of HM Prison Slade’s wiliest character, and Kate Beckinsale, daughter of Richard (Godber), reminds us that the series really clicked when it became a two-hander. It’s a total treat for devotees of the kind of comedy where not a word was wasted. David “Old Man Blanco” Jason is the narrator.