'Operation Mincemeat': Colin Firth and Matthew Macfadyen on their 'unlikely pairing' in new WW2 drama

Watch: Colin Firth and Matthew Macfadyen talk Operation Mincemeat

Colin Firth and Matthew Macfadyen have credited Michelle Ashford's script for their unique chemistry in Second World War thriller Operation Mincemeat.

Firth plays real life naval intelligence officer Ewen Montagu in the film, alongside Macfadyen as grounded flight lieutenant Charles Cholmondeley.

The film follows the duo as they help to put together the titular deception operation, using a corpse carrying false documents to dupe Germany into moving forces away from Sicily in order to repel a fake attack via Greece.

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Firth told Yahoo that the chemistry between the duo — who both famously played Mr Darcy in different adaptations of Pride & Prejudice — was "on the page" in Ashford's script and was helped by the fact he and Macfadyen "got on well very quickly and very early on".

Macfadyen added that the characters were "an unlikely pairing of intelligence officers", which added to the unique feel of the movie.

He said: "Montagu was very urbane, came from an enormously wealthy family and had this sort of wonderful life.

"Cholmondeley was a sort of oddbod, who was a frustrated pilot and couldn't be a pilot because his eyesight was too bad. He probably couldn't fit in the cockpit because he was quite ungainly and tall."

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Macfadyen described this take on the war movie as being unique in its focus away from the battlefield, involving characters who approached their work with humour as well as seriousness.

He said: "You were aware of how disciplined and determined and serious they were but also they were aware they might die the next day. London was being bombed and there was a surrealness about the war.

"They were able to find humour and laugh at themselves. There was an awful lot of enjoyment because they were good at it."

Historical tales of this sort of unique brand have been a staple of the British film industry for decades and Penelope Wilton, who plays Hester Leggett in the movie, said the UK excels in the genre "because we've got a lot of history".

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She said: "I think that we're interested in getting things right. We go into the detail. I've done a number of things where there has been a lot of historical input.

"I don't know why we do them better than anyone else, but we perhaps don't have to make great flourishes. We can tell the real story when we get the chance."

Director John Madden, shooting from Ashford's dramatisation of Ben Macintyre's non-fiction book about the operation, said he thought the story had clear cinematic potential.

He said: "It's about a hidden war. It's about a war where you're gaming ideas and creating a kind of fictional environment which allows you to pass certain messages and so forth.

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"That seemed really fascinating and cinematically interesting because you're constantly contrasting a literally subterranean word where people are in a room creating a fiction with a war that is raging across the other side of the world and which the population of London had become very used to."

Macintyre added that the full machinations of Mincemeat were "highly complicated" and too nuanced for a film to depict in totality, but he said Madden's work was able to "fill in the emotional gaps".

The historian said: "What made the real Mincemeat story so extraordinary is that these people not only created this world, but began to inhabit it themselves.

"The distinction between their own lives and the life they were creating began to get blurred and merge. To reproduce that in film is an alchemy that is absolutely extraordinary, I think."

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The film is blessed with a glittering ensemble cast, including Kelly Macdonald, Mark Gatiss, the late Paul Ritter and The Death of Stalin actor Simon Russell Beale as Winston Churchill.

Jason Isaacs appears in the film as Admiral John Godfrey, whose assistant is future James Bond author Ian Fleming (Johnny Flynn), and he said the stranger-than-fiction story drew him in.

"I just thought it was a cracking story and not one that I knew," said the Harry Potter actor.

Isaacs added: "I knew the headline, but [I loved] to be taken inside the detail and the brilliance and the bravery and the audaciousness of this spycraft and disinformation project."

For Macfadyen, part of the joy of the story was in the way such an over-cranked and bizarre scheme played such a pivotal role in a conflict that played such a defining part in history.

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The star said: "It's quite cerebral, isn't it? They thought the war. They were a collection of deeply bright and creative lateral thinkers, inventing ruses and misinformation and ploys to foil the Axis powers."

Operation Mincemeat will arrive in cinemas across the UK from 15 April.

Watch: Trailer for Operation Mincemeat