Though Laurence Olivier flirted with Russian and French-Canadian accents in his earlier films (Demi-Paradise and The 49th Parallel), and famously portrayed Othello with his deep, African-Caribbean tones, he really hit his stride in the 1970's. His chilling portrayal of Nazi dentist Szell in Marathon Man gave us the clipped and precise German accent and the memorable phrase, "Is it safe?"
Two years later, he would give us Ezra Lieberman, the Simon Wiesenthal stand-in, in 1978's The Boys From Brazil. He began to take more and more character roles like these, and sadly, the accents used in each began to sound much the same as one another. The French con artist in A Little Romance, the Dutch Abraham Van Helsing of Dracula, and the Yiddish Cantor Rabinovitch of The Jazz Singer were somewhat indistinguishable.
Olivier's American accents often accompanied performances so hammy that the audience almost needed mustard - the southern patriarch of The Betsy, and Douglas MacArthur in the ill-conceived Inchon. Only when he returned to his native accent, even in such films as Clash of the Titans, were we not distracted by his attempts to authentically replicate his character's regional American accents.
The last non-British accent he would offer would be an American Jewish accent in Mr. Halpern and Mr. Johnson, an HBO telefilm costarring Jackie Gleason.