With Apocalypse Now set to shoot outside of the States for a gargantuan 17 weeks, Steve McQueen declined an invitation to play the lead role of Willard. Al Pacino also turned down a role after concerns about falling ill in the jungle again – as he had done while shooting Godfather Part II.

After these setbacks, Coppola recalled a young actor who had read for the part of Michael during casting of The Godfather, and invited him to play Willard. That actor was Martin Sheen.

As (typically bad) luck would have it, Sheen was already committed to another movie, and Coppola settled for Harvey Keitel in the role instead. Meanwhile, the erstwhile director managed to secure the film’s biggest asset, Marlon Brando, by dangling a giant juicy carrot in front of him. A carrot that cost $3.5m.

Rounding out the principal cast, Dennis Hopper was brought in, though at this point he had no idea what his part would end up being. The movie’s final scenes had yet to be properly written by Coppola...