Welch won the annual Carnegie Medal from the Library Association, recognising the year's best children's book by a British subject.

Guy of Lusignan, the charming but weak-willed King of Jerusalem, is swayed by poor advice to march the assembled forces of Outremer to the relief of the city across a waterless plain at the height of summer.

He learns from his squire's father that his family's castle at Llanstephan has been taken by an ally of Prince John's and leads a raiding party to win it back.

A notable aspect of the book is the bringing into contrast of the refinements of the medieval Islamic civilisation, which had been adopted by the Outremer noblemen, with the comparatively stark and crude European living conditions of the time, and the suggestion that the returning Crusaders brought Eastern standards of luxury and culture to the West.

[2] In The Nesbit Tradition, Marcus Crouch describes Knight Crusader as Welch's finest book: "a highly competent piece of writing, the historical detail tightly integrated with the subject matter, the narrative economical and very brisk.

However, he criticises its lack of selectivity: "Welch was so keen to put all he knew and felt about the Crusades into his book that he dissipated his effects and left a string of loose ends.