Widow of a Duke
Officially the widow of a duke is known as 'The Dowager Duchess of Mayfair' (unless there is already a dowager duchess in that family still living in which case the widow of the junior duke is known by her forename, eg Anne, Duchess of Mayfair).
In practice, many widows prefer to use their forename in place of 'Dowager'. If in doubt, use of the forename is recommended.
If the present holder of the dukedom is unmarried, the widow of the previous duke does not use the term of either The Dowager Duchess of Mayfair, or Anne, Duchess of Mayfair, but continues to be known as The Duchess of Mayfair.
How to address the Widow of a Duke:
|Beginning of letter||Dear Duchess|
|End of letter||Yours sincerely|
|Envelope||The Dowager (or Anne) Duchess of Mayfair|
|Invitation||The Dowager (or Anne) Duchess of Mayfair|
|Description in conversation||The Duchess of Mayfair|
|List of Directors or Patrons||The Dowager (or Anne) Duchess of Mayfair|
|Place card||The Dowager (or Anne) Duchess of Mayfair|
|Legal document||The Most Noble Anne Mary Teresa Duchess of Mayfair|