The story behind the making of the film and the religious storm it caused are the subject of Holy Flying Circus

As Brian Cohen, the hapless hero of Monty Python's Life of Brian, finds out, it can be tricky stepping into the shoes of someone worshipped by all. And the fear of not passing muster is on the minds of all six actors cast as Pythons for a BBC comedy drama about the release of the film in 1979.

Holy Flying Circus will tell the story of the making of Life of Brian and the righteous fury that surrounded the release of its satirical take on the gospels. It is the first attempt to dramatise the activities of the sextet who transformed the nature of comedy in this country and produced a British film now critically regarded as one of the very best.

Coming together this summer to play Michael Palin, John Cleese, Terry Jones, Eric Idle, Terry Gilliam and the late Graham Chapman, the performers have admitted to feeling odd about playing men who have the status, if not of modern-day messiahs, then at least of comedy gods for their fans around the world.

During the filming of BBC4's Holy Flying Circus, which is written by Tony Roche, co-writer of In the Loop and The Thick of It, its stars were initially wary of impersonating such famous comics. "We wanted to be affectionate about the Pythons and we all had a sense they were our comedy heroes," said director Owen Harris. "You could feel the anxiety in the room when the actors got together in character for the first time. We had a room full of Pythons."

Harris, who has previously directed the hit series Misfits, encouraged the actors not to worry too much about portraying their characters authentically. "We didn't want impersonators, although in the end we have got an amazing set of Pythons. I don't know what the originals will think. They will all be seeing it for the first time when it goes out next month," he said.

Comedian and writer Steve Punt, who plays Idle, found the humour of Roche's screenplay guided the performances. "When you are playing someone who is not only an icon of comedy, but who is still alive, it does feel pretty strange. But the secret is the script. It is funny and not at all a forensic depiction of the people. It captures the spirit of the Pythons."

Darren Boyd, star of Case Sensitive, plays Cleese and has tweeted about how odd it felt to stand in a street "doing the silly walk" or thrashing things with a stick "a la Fawlty Towers". But happily for Boyd, encouragement came down from on high. Stephen Fry, who makes a cameo appearance as God in the film, offered support on set. "God just gave me his blessing regarding my Cleese 'look'. He was most enthusiastic. My life is complete," tweeted Boyd.

Next, one of the original Pythons, Terry Jones, gave the actor who plays him a remote blessing via Twitter. When Rufus Jones messaged him to say he was playing him in a BBC4 drama, the Python replied that his efforts were "all in a good cause". This weekend the 69-year-old, who directed Life of Brian, told the Observer he "loved the script" of the new production. "It is a wild flight of fancy and I am keeping my fingers crossed about how I am played," Jones said.

Canadian comic Phil Nichol plays Gilliam, while Charles Edwards plays Michael Palin and Tom Fisher plays Graham Chapman, the most laconic Python, who died of cancer in 1989 aged 48.

Unlike other recent BBC4 docu-dramas about comedians, such as Tony Hancock and Hattie Jacques, Holy Flying Circus aims to be a comedy in its own right. "It has a very different tone from other films in that strand," said Harris. "We are calling it a fantastical reimagining." Inspired by Python, the director said the film tells its story in an unorthodox way. "It is non-linear for a start, and has animation in it, like Terry Gilliam's work. We took his drawings as a starting point and then applied our own craft. In the end some of the sequences are rather like the American cartoon Family Guy, although not visually."

The new drama centres on a notorious television confrontation that took place on 9 November 1979 between two of the Pythons, Cleese and Palin, and the Roman Catholic writer and broadcaster Malcolm Muggeridge, who believed that Life of Brian was a weak and scurrilous attack on Christianity. At Muggeridge's side for the debate on the BBC2 show Friday Night, Saturday Morning was the Bishop of Southwark, Mervyn Stockwood.

"You might say Holy Flying Circus is a comedy equivalent of the film Frost/Nixon, marking a historic TV moment, but that was much more factual and we are playful, although the debate itself is verbatim," explained Harris.

"I do wonder whether viewers will realise that, because some of it is quite extraordinary."

Although Life of Brian was a box-office success, it was met with a volley of international protest from religious groups. Thirty-nine British local authorities imposed some sort of ban. The plot centres on the unfortunate chain of events that follow the mistaken identification of a young Judean man as a new religious leader. Reluctant to the last, Cohen, played by Chapman, is tragically unable to clarify the misunderstanding.

During the TV debate, chaired by the lyricist Tim Rice, Muggeridge called the film "squalid" and "tenth rate". The bishop levelled some low blows too, accusing the film of being "fourth form revue" standard and implying the Pythons were "mentally deficient".

"It was a clash of cultures. Palin became quite frustrated, but both he and Cleese remained respectful. But the respect wasn't returned," said Harris.

Terry Jones too, remains annoyed by Muggeridge. "It was quite a cheek because he had missed the opening of the film," he said. "They had a good lunch and then arrived late at the viewing theatre that day."