Peter O’Toole as Henry II in The Lion in Winter and Becket
Charles Gray as Mycroft Holmes in The Seven Per Cent Solution and the Grenada/WGBH Sherlock Holmes
Frank Finlay as Inspector Lestrade in A Study in Terror and Murder by Decree (both about Sherlock Holmes vs. Jack the Ripper!)
William Daniels as John Adams in 1776 and The Rebels
Herbert Lom as Napoleon Bonaparte in Young Mr. Pitt and War and Peace
Christopher Lee as Count Dracula in Terror of Dracula and a host of other Hammer films, and in Jess Franco’s unrelatedCount Dracula
I’m sure there are plenty of others. I know of others.