In the case of sons of a duke or marquess who by courtesy have Lord prefixed to their given and family name the wife is known by the husband s given and family name with Lady prefixed e g The Lady John Smith the daughters of dukes marquesses and earls are by courtesy Ladies here that title is prefixed to the given and family name of the lady e g The Lady Jane Smith and this is preserved if the lady marries a commoner e g Mr John and The Lady Jane Smith The predicate The should be used prior to Lady or Lord in all cases except after a divorce for women who do not hold the courtesy title of Lady in their own right e g Heather Lady McCartney or Jane Lady Smith as the ex wife of The Lord John Smith