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