The Sword in The Stone by T. H. White, the first book of The Once and Future King, is a novel about a young boy named Wart (who, as we suspect all along, but only find out for sure at the end, is actually the future King Arthur) who befriends a magician named Merlyn. It was published in 1938. ...

The version appearing in 1959 in the tetralogy was substantially revised, partly to incorporate events and themes that White had originally intended to cover in a fifth volume (which was finally published after his death, as The Book of Merlyn). To this end, the revised version includes several new sequences and leaves out some of the sequences that had appeared in the original (notably the sequence that was the basis of the Mad Madam Mim scenes in the Disney film).

However, the consensus of critical opinion is that the revised version was actually inferior to the original. Publishers have more recently gone back to using the original version, at least when it is published independently of the tetralogy.

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A BBC radio adaptation in 1982 starred Michael Hordern as Merlyn. Hordern had already starred as another great literary wizard, Tolkien's Gandalf, in the BBC's Lord of the Rings (1981).