John Bernard Adie Barton, Commander of the Most Excellent Order of the British Empire, and co-founder of the Royal Shakespeare Company, is magnificent in this, portraying (and narrating as) Sir Thomas Malory, knight prisoner. The other actors have no lines; it is both literally and figuratively what Shakespeare called a dumb show. Jeremy Brett does show some relevant facial expressions as King Arthur, but David Robb as Sir Lancelot shows Pythonesque levels of stupidity, at one point failing to don armor when the narration (and common sense) twice command him to do so. But Barton is always worth listening to, and worth watching whenever he is on screen. Barton revealed aspects of both Sir Tom and King Arthur new to me, and I've read and reread both the Winchester and Caxton texts of Malory, not to mention White and Lerner and Lowe.
So I urge you to listen to this, even if you don't watch it. It seems only available on the Broadway HD streaming channel, though Barton is listed as "Creator" of a rare audio-book adaptation of Le Morte d'Arthur around the same time, with actors including William Squire, Tony White, and Harry Andrews: Musical Heritage Society MHS 834985F.