Allied interview: Marion Cotillard on helping Brad Pitt perfect his French accent

The pair star as spies who fall in love while deep undercover in French Morocco, at the height of the Second World War

Allied gives star Marion Cotillard a rare opportunity - allowing the French actress to speak both in English and in her native tongue over the course of the film.

She plays spy Marianne Beausejour, who meets with Max Vatan (Brad Pitt) in French Morocco to pose as a married couple; the perfect ruse to carry out their assassination plan at a planned ambassadorial reception.

And, as always happens in the movies, their pretend affair soon transforms into a real one; the spark for legendary director Robert Zemeckis (Forrest Gump, Cast Away)'s first foray into the genre of wartime romance, one that stirs in the thrills of espionage for good measure.

Settling in London to start a family amongst the terror of the Blitz, Marianne and Max's marriage is thrown into turmoil when one of them come under suspicion for treason; is a love born out of an elaborate lie one which can stand the test of time? Can their trust in each other overcome the pressures of war?

Cotillard's role as Marianne may have allowed her to speak French during her undercover scenes in Morocco - but that also meant her co-star Pitt had to put his best French accent to the test, though his character is remorselessly teased for his Canadian lilt making him sound like a "Québécois". We spoke to the actress about Pitt's tackling of the language, and whether she ended up coaching him on set.

Allied hits UK cinemas on 25 November.