So runs the usual response to a movie adaptation – stuff gets cut, favourite scenes left out, it’s just not how you imagined it. So it’s unusual to be given a script and asked to turn it into a novel.

After a millennium of mystical and/or pious Arthurian lore, someone — could it have been Guy Ritchie? — determined that the once and future king needed the Guy Ritchie treatment. But then someone — ...