Royal dukedoms in the United Kingdom
In the British peerage, a royal duke is a member of the British royal family, entitled to the titular dignity of prince and the style of "His Royal Highness" who holds a dukedom. Dukedoms are the highest titles in the British roll of peerage and the holders of these particular dukedoms are Princes of the Blood Royal. The holders of the dukedoms are royal not the titles themselves. They are titles created and bestowed on legitimate sons and male-line grandsons of the British monarch, usually upon reaching their majority or marriage. The titles can be inherited but cease to be called "royal" once they pass beyond the grandsons of a monarch. As with any peerage, once the title becomes extinct, it may subsequently be recreated by the reigning monarch at any time.
Earl of Shrewsbury
Lord Shrewsbury is the senior earl on the Roll in the Peerage of England (the more senior earldom of Arundel being held by the Duke of Norfolk). The earldom of Waterford is sometimes called the "Premier Earldom of Ireland "on the Roll"", as the oldest Irish earldom, that of Kildare, has been a subsidiary title of the Duke of Leinster for centuries and the Earl held the oldest Irish earldom held by anyone ranked as an Earl. If the Viscount Mountgarret proves his presumed claim to the 1328 earldom of Ormonde, the Earls of Shrewsbury would lose this distinction, but they derive higher precedence from their English earldom in any event. Despite holding three differently named earldoms Lord Shrewsbury is always styled simply "The Earl of Shrewsbury".