My Department's guidance on section 37 (which is published at http://www.foi.gov.uk/guidance/exguide/sec37/annex_a.htm) contains a list of members of the royal family since 1 January 1975 (as at June 2004) comprising those entitled to use the title Majesty or Royal Highness and their spouses (since 1 January 1975). The list will change over time, especially through marriage or birth. This guidance was published in June 2004 and when it is next updated it will include newer members of the royal family such as the Duchess of Cornwall.