Malory based the first tale of his Morte Darthur on an unusual version of a very popular romance, the thirteenth-century Old French prose Merlin. The romance falls into two parts. The first, which we may call the Merlin proper, tells the story of Merlin’s life and the wonders he works in a legendary Britain up to Arthur’s coronation, which he is instrumental in bringing about. The second part is a continuation, or Suite, which tells the story of the early years of Arthur’s reign, when he establishes his kingdom, and some of his most famous knights make their reputations. Merlin again has a notable role.

The popular, or ‘vulgate’, version of the Merlin is the second of the five parts of the Vulgate Cycle, the best-known version of the Arthurian legend in the Middle Ages. The Vulgate Merlin survives in nearly fifty French manuscripts, and was translated into Italian, Dutch, and Middle English. Although Malory seems to have known and occasionally used this Merlin, he based his first tale on its obscure literary cousin, the Post‑Vulgate Merlin, which is part of another cycle of romances, the Post-Vulgate Cycle or Roman du Graal, that combines material from the Vulgate Cycle and the Old French Prose Tristan into a narrative that focusses more on Arthur and the Grail than on the adventures of the Knights of the Round Table. The Post-Vulgate version of the Merlin proper is almost identical with the Vulgate version, but its Suite is very different. Since the Post-Vulgate Merlin survives only in three incomplete French manuscripts and half a dozen much smaller fragments, it is sometimes helpful to check the corresponding Hispanic Post-Vulgate texts to see what mediaeval French versions are likely to have said at textually difficult points. All the surviving Hispanic manuscripts are fragmentary, but the two early Spanish printed editions, the Baladro del sabio Merlin, published in Burgos in 1498, and the Demanda del sancto Grial, published in Seville in 1535, are both complete.

Malory began his story late in the Post-Vulgate Merlin proper, with the first meeting between Arthur’s future parents, and followed it to its end, Arthur’s coronation. In the longest surviving manuscript of the Post-Vulgate Suite, Cambridge University Library, Additional 7071, Arthur’s coronation is followed by an episode of which there is no trace in any of the other surviving Post-Vulgate texts.