Actor Colin Firth has said he felt ''a little overwhelmed'' by the enormity of the story to be told in his latest film The Railway Man.

The Oscar winner plays Eric Lomax, one of thousands of Allied prisoners of war forced to work on the construction of the Thai/Burma railway during the Second World War.

Years later, still haunted by memories of the torture and brutality he endured, he meets the beautiful Patti, played by Nicole Kidman, who tries to help him.

Shooting begins on April 30 in Scotland, where Lomax was from, and will later move to Thailand and Queensland, Australia.

Firth has met Eric and Patti Lomax twice, and said the meetings helped prepare him for the role.

He said: ''They are both incredibly engaging and made me feel very welcome.

''I found them both a delight, though I did feel at times a little overwhelmed by the enormity of the story.

''It was important to me to meet them, it focused me and it was something that was very sobering, but also the story is such a big one and about a generation prior to my own, it can feel a bit abstract, a little bit out of reach, but to meet Eric personalised it and humanised it.''

Firth suggested the character is a man who does not know where he is going as he deals with the emotional fall-out of his wartime experience.

He said: ''He is looking for a way home that might be represented by Patti.''

Kidman is ''polishing'' her English accent to take on the role of Patti, who is English, and plans to meet her during shooting as she has not yet done so.

The Oscar winner is looking forward to rediscovering Scotland and Edinburgh during the shoot, having visited the country as a teenager.

She said: ''I did a road trip with a boyfriend when I was 18, so it has been a while, but I went all the way up to Ullapool.

''The great thing about being an actress is you get to live in a city for a certain amount of time, so that's what I look forward to.

''I've heard there's some great restaurants, so I will be out and about, though we're working six days a week.''

The film also features War Horse star Jeremy Irvine, Stellan Skarsgard, of The Girl With The Dragon Tattoo, and Japanese star Hiroyuki Sanada.

Asked how he felt to play the young Colin Firth in the film, Irvine replied: ''You find yourself looking in the mirror going 'Am I quite up to that?' It is a great privilege to be working with actors like this.

''I'm so early in all this and still desperately trying to learn and use these people as role models.''

Shooting will take place at locations including Edinburgh and North Berwick.

Director Jonathan Teplitzky said it was important to film in Scotland.

He said: ''We are all captured by the story and Eric's journey, and I think it's a story that began here and, to a certain extent, we just wanted to honour that and capture the story of his journey.

''Him being from this part of the world, it seemed like a great place to start the journey we are going on.''

The film is an Australia/UK co-production between Pictures In Paradise and Archer Street.

It is backed by Screen Australia in association with Silver Reel, Screen Queensland, Creative Scotland and Lionsgate UK.