Kenneth Branagh had to stab dead animals to get into character for 'Murder on the Orient Express'.

The 56-year-old actor, who portrays Detective Hercule Poirot in the mystery film, has admitted to get into character he had to plunge a knife into the organs of deceased creatures to help him understand murder is not a game but a ''mechanical act''.

Speaking about his preparation for the role, the 'Hamlet' star said: ''One of the things I did early on was get a knife - this was all under instruction from a safety expert - and plunge it into the organs of some animals. They were dead. In order to go into the idea of steel in flesh being a really difficult thing to do. The idea of murder not being a game but involving a horrible mechanical act.

''If you're a stranger to it, the act of killing is a weird one. I kept trying to shake myself out of any sense this was a board game or drawing room mystery. Instead, this was about a dark dirty act that you need to know the reality of.

''What it's like to lose people and what grief does to people. It can turn them very powerfully in terms of an emotional reaction. All of that was to set up a danger and volatility on this train that was a million miles away from heritage, biscuit tin, pantomimic, drawing room mystery.

''Directors and detectives, in as much as they have any connection, both seek truth. They look into the eyes of people they're interviewing and want to understand whether they can believe them.''

Branagh also worked closely with a dialect coach and learned French to help him achieve an authentic accent.

He explained: ''I don't speak other languages so learning to speak in a French accent meant trying to learn to speak French to begin with, then how to speak French with a Walloonian accent, then with a Walloonian accent of a man born in Spa, who lives in London. All of that was quite specific. Otherwise you could be generic and sound like Inspector Clueso. He's not that. Everything about it had to have as much detail as possible.''

The movie legend believes ''90 per cent'' of a film's success in the casting, and he believes as soon as Dame Judi Dench confirmed her role in the movie it was a ''magnet'' for other stars to agree to be cast in the production.

He told the New Zealand Herald Online: ''We literally started with Judi Dench who seemed to me great casting for Princess Dragomiroff, she's great casting for anything. I knew she would enjoy this imperious superior character because it's very far away from who she is and she likes to play surprises.

''Judi became a magnet for the other people. People like Johnny Depp and Michelle Pfeiffer were completely in love with Judi and when they came on board that was a domino effect.

''Ninety per cent of the success of a film like this is the casting because aside from the big landscape, which we try to exploit, the other forensic landscape in a 70mm version of a crime procedural is the human face. So you want people who can be there, hold the screen, hold your attention. Whom you are interested to watch think.''