Awhile ago we saw The Devil's Disciple (1959), with Burt Lancaster, Kirk Douglas, Laurence Olivier, and Janette Scott. Aside from Scott's role being pretty pathetic, and a ridiculous action sequence, it was pretty good. They changed a few things, but it was generally faithful to George Bernard Shaw's play. However, the play does a better job of explaining Scott's character. In speaking of the American rebels, Olivier's Burgoyne says,

Martyrdom, sir, is what these people like: it is the only way in which a man can become famous without ability.

Nice line. It was also interesting to see that the historical Burgoyne was himself a playright.