Sure, he also became known for playing a definitive Sherlock Holmes, but judging by most of the movies I've seen him in (see list at right), he was mostly known for playing a cad.
Anna Karenina: he is Karenin, the cold husband.
David Copperfield: he is Murdstone, the cold stepfather.
The Adventures of Robin Hood: he is Sir Guy, the bad guy who dies in the climactic sword fight with Errol Flynn.
Captain Blood: he is LeVasseur, the pirate who dies in a sword fight with Errol Flynn.
I haven't seen the movie or read the book, but I'm sure that his role in A Tale of Two Cities is also unsavory. According to the Internet Movie Database, he played the bad guy so often that he only won one sword fight during his entire 40+ year film career.
He does have that pursed lip thing down, though. And looks so nasty with a Vandyke beard.