In the 1970s, Charles Bronson was the most famous man in Hollywood. While this iconic action star has gone down in cinema history for his devil-may-care quips and awe-inspiring stunts, his steely-eyed stare concealed an utterly brutal past.

Bronson was the strong silent type—but filming one scene in The Great Escape nearly made him break down. Bronson had a brutal childhood working in coal mines to support his family, so having to go into tight enclosed spaces as Danny the Tunnel Rat brought back harrowing memories.

Bronson developed horrible claustrophobia as a child, and as he filmed the classic movie, his fear came rushing back.