Trebuchet alone had foreknowledge of the perilous occasion on which this splendid weapon would break, and he alone would be able to mend it. The context suggests that he may have had some personal acquaintance with the Fisher King's niece, who sent the sword to her uncle.
Trebuchet also carved engravings on King Frimutel's sword and Duke Orguelleus of Lalander had a fine helmet crafted by the smith.
Despite his name, which sounds both Cornish and French, Trebuchet lived near Cotoatre, identified with the Firth of Forth. A connection has been suggested with Turbe, father of the Irish smith god, Gobniu.
Trebuchet forged this as one of only three swords he was ever to make in his life: this sounds like a deliberate decision on his part, since he apparently survived the making of the last sword by some time. Why the fact of his making so few swords should enhance their value puzzles me, but perhaps I am too steeped in the idea that long experience and practice produces the best work; perhaps Trebuchet had honed his skill on other types of smithery.
In any case, this remarkable and guaranteed-unique sword was notably light for its size and strength. It seems to have had but a single flaw: it was predestined to break on one occasion, and only one, but on that occasion its wielder's life would be at stake. Its shattering, however, would not necessarily result in the bearers death (though it would clearly test his survival skills).
How the Fisher King's niece obtained the sword from its maker is not told, but she sent it to her uncle with the request that he pass it on to a worthy recipient. Percivale having just arrived, and not yet having failed to ask the right questions about the Grail, the Fisher King presented it to him. Next day, seeing him wearing it, the niece explained to him how, when it broke, he would be able to get it repaired - but only by carrying the pieces back to Trebuchet at Cotoatre. There is a possibility that the sword broke during Percivale's fight with the Haughty Knight of the Heath, but the authenticity of this passage lies under the serious question.
Perceval happened upon Trebuchet's smithy while seeking someone to extraxt a nail from his horse's hoof. Trebuchet repaired the broken Grail Sword and reluctantly returned it to Perceval - as he was fated to die after he had repaired the sword.
This sword's pommel was gold and its sheath bore Venetian embroidery - trappings worthy of a mystical, magical blade with only that one tiny defect. Its baldric being worth a fortune makes me wonder if there should be any connection between this weapon and the Sword with the Strange Baldric mentioned later in the same romance.