Oscar-winner Firth’s costume for The Railway Man – in which he stars as Edinburgh-born prisoner of war Eric Lomax – included a natty moustache and pair of glasses.
Pride and Prejudice star Firth was seen walking in and out of a make-up trailer in the Craigmillar area yesterday.
One onlooker said: “We couldn’t get close to the building because it was fenced off. But we saw Colin Firth come out of the building and he went into a trailer for about two hours.
“He was in costume and we gave him a wave, but he looked a bit grumpy. Maybe it was the weather.”
The film also stars Nicole Kidman, who is expected to arrive on set today. The Australian plays Lomax’s wife. And film crews are due to head to North Berwick next month to shoot scenes for the movie.
Mr Lomax, now 92, served as a British Army signals officer during the Second World War and was held in the notorious Changi PoW camp after the fall of Singapore in 1942.