Never-before-heard Monty Python jokes are to be broadcast for the first time as the comedy troupe celebrate their 50th anniversary.

Michael Palin has produced five new programmes for BBC Radio 4 featuring the previously unheard material, drawn from the Python archives.

They will form part of a series of events and new releases to mark the group’s half century. The first episode of Monty Python’s Flying Circus first aired on BBC One on October 5 1969.

Explaining their enduring appeal, the comedians said: “Python has survived because we live in an increasingly Pythonesque world. Extreme silliness seems more relevant now than it ever was.”

The celebrations will begin in September with a season at the British Film Institute, including a marathon screening of 45 back-to-back Flying Circus episodes across two days - each session lasting 12 hours.

The BFI will also show “oddities and rarities” from the archive including corporate videos, public information films, guest appearances, charity spots, and a chance to see some of Palin’s own 8mm film from the Python film sets.

A teaser for the Radio 4 programmes, also to be broadcast in September, said they will reveal “the extra unpleasant things” planned for Brave Sir Robin, Eric Idle’s character from Monty Python and the Holy Grail, and “what John [Cleese]’s mother thought about her care home”.