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.
Baron Willoughby of Parham
Baron Willoughby of Parham was a title in the Peerage of England with two creations. The first creation was for Sir William Willoughby who was raised to the peerage under letters patent in 1547, with the remainder to his heirs male of body. The second creation was by writ in 1679, without the restriction on inheritance by gender. The creation of the barony gave right to an hereditary peerage and seat in the House of Lords, the upper house of Parliament.