Smash hit and cult classic 1975 comedy film Monty Python And The Holy Grail is to be re-released in cinemas to mark its 40th anniversary.

For one night only, on Wednesday 14th October 2015, the film will screen in 500 UK cinemas, in both its original and a brand new sing-a-long format.

The screening will be accompanied by a specially filmed, exclusive introduction from surviving Pythons Terry Jones, Terry Gilliam, Michael Palin, Eric Idle and John Cleese.

The film companies behind the re-release say: "We want to make this a fun event and are encouraging audiences to come along dressed up as their favourite character," and also promise an interactive social media campaign around the hashtag #holygrail40.

Here's the trailer for the re-release, with new voiceovers from Terry Jones and Michael Palin.

A brand new 40th anniversary special edition Blu-ray will be released by Sony Pictures Home Entertainment in mid-October. This is in addition to the Steelbook edition, which was released in June.

Here's an 'unboxing' video of the new special edition boxset, featuring the stars themselves: