The original usage of Mountbatten-Windsor was supposed to refer to those descendants of the Queen who do not hold Royal ranks or titles themselves but this has often still been used by those who do! However the royal house is still simply Windsor whether or not individuals like to add the Mountbatten bit themselves.

Well well I never read anywhere before about William IV being double barreled with St Andrews! One lives and learns!

Which of the "aura's" though? The one about Albert Victor being Jack the Ripper or the one about him liking certain establishments that catered for gentlemen of certain tastes? Another Clarence was drowned in a butt of Malmsey wine as I recall from Shakespeare.

A Duchess may use her first name but someone who is not a Princess in their own right derives the title from their husband. Where the husband is a Prince but not a Duke (such as Prince Michael of Kent who is a younger brother of the Duke of Kent but still entitled to the rank of Prince as a grandson of a Sovereign in the male line) then the name of the husband is indeed used following the Princess bit. Where a current Royal Duchess is concerned it is more usual to simply say "The Duchess of X" just as it is more usual to simply say "The Duke of X". Thus we have The Duchess of Cornwall and never Princess Camilla. It is different again with a Queen Consort who will always be entitled to use their own name. It is also the entitlement of the wife of the Heir to the Throne to use their own name as Princess this or that though again usually in this case it would be Princess of Wales.

Whilst Diana was still married to Charles she was referred to as either Princess Diana or The Princess of Wales. She only became "Diana, Princess of Wales" after the divorce which was in some ways weird as she was no longer royal and a non royal Princess is a rare thing!

Coming back to the Kents - the Duchess of Kent has stated that she does not wish to be addressed or referred to as an HRH but her personal wishes have no bearing upon her official title. The new Duke of Cambridge has long simply wished to be called "William" but this could be harder to maintain now.

It's going to be an interesting time for royal etiquette in the future I think!