The Affair of the Christmas Jewel is a book by Barrie Roberts and was published in 2002.
Summary[]
Flagged down by Inspector LaStrade of Scotland Yard as they walk through the icy winter streets, Holmes and Watson are transported to the home of the aristocratic Lady Whitebread. Once there, she tells them her traditional holiday centerpiece has vanished in the midst of the Christmas dinner - right under the very noses of her guests. The decoration? An enormous work of the jeweler's art centered upon a three inch round emerald called...the Christmas Jewel.