The Once and Future King
. But only if it were done SUPERBLY well. It'd have to be at least three movies, or maybe a really high-quality, high-budget miniseries. There have been enough ghastly King Arthur movies made already (Keira Knightley wearing bondage gear in the snow, anyone?).
There's one particular scene - where King Arthur is watching from the window as Lancelot rescues Guenevere from being burned at the stake, killing his friends in the process - that is just SO cinematic. It's painful and perfect - Arthur loves Guenevere and doesn't want her to die, and is hoping against hope that Lancelot, whom he also loves, will save her; but because of his commitment to justice he has to increase the guard, and even puts Lancelot's friends on the fighting line under the assumption Lancelot won't kill them. Lancelot, of course, wants to save Jenny because he loves her, and for reasons of chivalry, but is immensely guilty about having seduced the wife of his best friend, and
believes in justice (in theory). Guenevere, understandably, doesn't want to die and loves Lancelot, but recognises that by rescuing her Lancelot is dooming her husband - whom she also
loves - to starting a war that will split the kingdom and end in everyone's downfall. It's a horrible, tortuous situation, and TH White describes it so the pain just leaps off the page. With the right actors, it could be phenomenally heartbreaking.
That said, if I ever hear they're planning to make it into a movie I'll respond with scowling and suspicion.
I can't think of a single director who I'd trust to do the job... although I wouldn't mind Fran Walsh having a hand in the script.