Clint Eastwood has cast three real-life heroes as themselves in his next movie.

The 87-year-old filmmaker has enlisted Anthony Sadler, Alek Skarlatos and Spencer Stone to tell their own story of overpowering a terrorist on board a train from Brussels to Paris in 2015.

The movie is based on the trio's book they co-wrote with Jeffrey E. Stern, 'The 15:17 To Paris: The True Story Of A Terrorist, A Train, And Three American Heroes', which tells how Anthony, Oregon National Guard member Alek and Spencer - a US Air Force airman who was trained in martial arts - were travelling to Paris when an ISIS terrorist, armed with a loaded gun and ammo, boarded the vehicle with the intention of killing as many people as possible. The three Americans charged at the man and were able to overpower him as he prepared to launch his attack.

Jenna Fischer, Judy Greer and Ray Corasani will also appear in the movie, while various younger versions of the three men will be played by Paul-Mikél Williams, Max Ivutin, Bryce Gheisar, Cole Eichenberger and William Jennings.

The acting newcomers will expect to be worked hard as Tom Hanks - who had the lead role in 'Sully: Miracle on the Hudson' - recently admitted Clint treats his actors "like horses".

He said of working with the actor-turned-director: "You certainly don't want one of those Eastwood looks.

"He treats his actors like horses because when he did the 60s series 'Rawhide', the director would shout 'Action!' and all the horses bolted. So when he's in charge, he says in a really quiet soft voice, 'All right, go ahead,' and instead of shouting 'Cut!' he says 'That's enough of that.' It's intimidating as hell!"