BOOK REVIEW: A Jewel in the Crown: The Secret Churchill Files. The Reviewer — Mark Davidson is a Cipher Brief Expert and a retired CIA operations officer with multiple tours as Chief of Station and field leader. Mark writes the Chalk Marks column for The Cipher Brief, an exploration of the intersection of espionage, intelligence and popular culture. Mark currently serves as the Director of Business Resilience and Intelligence and Executive Protection for The Starbucks Coffee Company. He and his family live in Bellevue, Washington and Durango, Colorado. Mark can be reached at [email protected]