For a man with such extensive Shakespearian stage experience, Alec Guinness certainly didn't show movie audiences the depth of his talent. You can catch a few movies if you know where to look, but in general, his usual fare doesn't leave a lasting impression. Perhaps that was why he donned disguises so often; maybe he feared just being himself wasn't good enough? My hypothesis notwithstanding, you must know he wasn't knighted because of his work in Star Wars. If you want to see his real talent he kept bottled up for the rest of his film career, find the forgotten drama The Prisoner.
It's a cat-and-mouse film with virtually two players: Alec Guinness and Jack Hawkins. Alec plays a cardinal arrested on suspicion of treason, and Jack plays the interrogator bent on extracting a confession. For political reasons, Jack and the men of his fictional fascist government need Alec to confess. If he dissolutions his followers, they'll be easier to control. To avoid Alec's martyrdom, Jack has to be very careful in his interrogation tactics.
Depending on your point of view of the story, either of the men could be considered the lead. With nearly equal screen time, it's a toss up. Alec is obviously the focus, as he's imprisoned and psychologically tortured; but Jack soon looks at his assignment as more than just a job and becomes obsessed with making Alec break. Both men do exactly what is asked of them in the script and show talents they didn't usually show in their other movies. Their timing, chemistry, and feed off each other's energy is very engaging, even if the genre doesn't usually appeal to you. I wasn't expecting to like the film, but I couldn't tear my eyes away. I can't count how many times I said, "I didn't know he had it in him," when Alec would scream or cry. Can you imagine Alec Guinness crying? Here at the Hot Toasty Rag, we love rewarding three types of performances: the "what does it take?" performance, the obscure performance, and the best performance of one's career. As Alec's falls in all three categories, we were very happy to honor him in 1955.