Although Hollywood gossip likes to focus more on the catty rivalries between its leading ladies than it does its leading men, there have been more than a few times in the history of the movies when male co-stars have clashed and fallen out. And few Hollywood A-list men clashed more than Steve McQueen and James Garner.

Quite what sparked the animosity between the pair is unclear, but after starring together in 1963’s The Great Escape, it soon emerged that the two men had taken something of a dislike to one another. In his 2011 memoirs, The Garner Files, Garner claimed that the disagreement stemmed from McQueen wrongly believing that he’d had an affair with his wife. (In fact, when it came to relationships, Garner was one of Hollywood’s most strait-laced stars, who remained happily married to his wife Lois for almost 58 years.)

The pair’s animosity finally came to a head in 1966. By then, McQueen had for several years been pitching an idea for a movie exploring the life of rival racing drivers, tentatively titled Day of the Champion. Garner, meanwhile, had been offered a part in a racing film of his own, called Grand Prix. Garner’s movie turned out to be one of the biggest hits of the year—forcing McQueen to shelve his idea for a further five years. (He eventually released it under the title Le Mans in 1971.)

Adding another dimension to their disagreement, Garner and McQueen owned neighboring apartments in Hollywood, and when Grand Prix turned out to be a hit, McQueen reportedly sought revenge on his downstairs neighbor by urinating on his balcony.

No wonder there was little love lost between the two of them…