I was not the world's biggest fan of Deborah Kerr. In the '50s and early '60s she was the most prestigious actress in Hollywood, the automatic choice for any Oscar-baiting film and herself an almost automatic Oscar nominee (though she didn't win any). But for that reason, a lot of her career consists of the airless, static "prestige" pictures that infested Hollywood in the post-television era. And there's something a little airless and static about some of her performances in these movies; sometimes she could seem too unspontaneous. When she played two parts that had previously been filmed by Irene Dunne -- in The King and I and An Affair to Remember -- she suffers by comparison with Dunne's naturalness and vitality.
That said, Kerr was always at least good and sometimes more than that. Her early work in British films, especially for Powell and Pressburger in The Life and Death of Colonel Blimp and Black Narcissus, has the very liveliness and naturalness that her American work didn't have; she was by no means the first or the last English actor to do better work in her own country. (Even her best later film, The Innocents, was actually a British production with a British cast and crew.) And even in her U.S. period, she could loosen up if she had the right director; in An Affair To Remember she adapted well to Leo McCarey's trademark improv (remember her improvising "What? I don't know, I thought you said something" with Cary Grant), which a lot of serious actors -- Paul Newman, for example -- couldn't do.