Sir Kenneth Branagh said Dame Judi Dench was a "critical component" for 'Murder on the Orient Express'.
The 56-year-old actor both starred and directed the new Agatha Christie remake, which sees him portray detective Hercule Poirot in the upcoming movie, and the movie icon has admitted the 82-year-old actress was the first person he cast in the film, before Johnny Depp, Michelle Pfeiffer, Penelope Cruz, Daisy Ridley, Josh Gad and Derek Jacobi.
Speaking to the Mirror newspaper, Branagh said: "They are a lovely group. A really critical component was Judi Dench, who was the first person I cast.
"I asked if she would do it and I hadn't finished the question when she said yes.
"Judi is a talismanic figure. Derek and Judi know each other from a thousand years ago. Johnny has worked with Judi and he worships her.
"She has trouble seeing, but she never complains."
The film follows a group of passengers on board a train travelling through Europe, who try to uncover who is the villain when a fellow traveller is murdered.
Although the story is well-known and has been made into a movie back in 1974, which saw Albert Finney portray Poirot, Branagh believes his version his different to any other production because he has "added some pieces" in order to make it unique.
He said: "It's still on a train and you still have many of the same characters, but we have added some pieces.
"Our inspiration comes from the novel but we have also raided some of the other Poirot books.
"I'll say this, there's mystery, but there is rage, loss, and grief underneath it all. Everyone has a story.
"We created as much paranoia and suspicion as we could. As for the end of the movie, the who and the how and the why become really important. The why gives us great suspense.
"We've had the chance to be inventive and imaginative about how the story goes, so there are some surprises."
And Branagh would "love" to make more films based around Christie's books.
He said: "I would love to make more films from Christie's books, although I'm sure we're not going to make 37 of them, which is how many we have to choose from."
Tagged in Johnny Depp Michelle Pfeiffer Dame Judi Dench