Possible Clues:

• Renowned escapologist
• Giant of magic history
• Subject of this puzzle (who has himself done a 39-Across)
• Entertainer who needed a get-out clause?
• Stage name of Ehrich Weiss, for whom the ends of 20-, 36- and 42-Across were props
• He could always get free hour in diary, organised after end of lunch
• Double-H of magic
• Master escaper