In this special film, Imagine... follows the surviving Pythons as they prepare for the reunion John Cleese dismissed as "absolutely impossible" and which Eric Idle joked would only happen "if Graham Chapman came back from the dead".

Instead, when tickets for a one-off show in London went on sale last November, they sold out in a staggering 43 seconds. Nine extra dates were added, all of which sold out, and then came offers from Australia and America. But the five remaining members (collective age 357) instead decided to bring down the curtain on Monty Python for good when this run of shows comes to a close.

In the 40 years since Flying Circus, each member has gone on to forge a successful solo career. John Cleese co-created Fawlty Towers, wrote A Fish Called Wanda and has just completed a live tour, Alimony, to pay for his latest divorce. Michael Palin has made hit travel shows, won a BAFTA Academy Fellowship Award, written numerous books and is set to publish his third volume of diaries. Terry Gilliam became a successful film director and is now setting his sights on opera as he prepares for a show at English National Opera. Terry Jones has written books, hosted television documentaries and is in the midst of directing his first feature film in 18 years - a comedy starring Simon Pegg and Kate Beckinsale. And finally, Eric Idle, the brains behind the reunion who wrote the global smash Spamalot, who has been pulling the strings from his home in Los Angeles to bring the London reunion show into existence.

Alan Yentob meets up with the Pythons as they pursue their individual projects, with exclusive access to the reunion rehearsal process.