Becket (1964)
O’Toole immediately followed up Lawrence of Arabia with Becket, the first of two films where he plays King Henry II (the second is also on this list — what can I say, I love a medieval drama!). The movie is based on a play by Jean Anilouh, which O’Toole was set to star in on the London stage before dropping out to take Lawrence of Arabia (Christopher Plummer took over). The dramatised take on real English history follows King Henry II and his longtime friend Thomas Becket (played here by Richard Burton) on opposite sides of a dispute with the church.
It’s two peers/drinking buddies working side by side, and they just happen to be some of the best actors of the decade.