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
In the Peerage of England, the Peerage of Great Britain, the Peerage of Ireland and the Peerage of the United Kingdom (but not in the Peerage of Scotland), barons form the lowest rank, placed immediately below viscounts. A woman of baronial rank has the title baroness. In the Kingdom of England, the medieval Latin word ", baronis" was used originally to denote a tenant-in-chief of the early Norman kings who held his lands by the feudal tenure of "barony" (in Latin "per baroniam"), and who was entitled to attend the Great Council (Magnum Concilium) which by the 13th century had developed into the Parliament of England.
Feudal baronies (or "baronies by tenure") are now obsolete in England and without any legal force but any such historical titles are held "in gross", that is to say are deemed to be enveloped within a more modern extant peerage title also held by the holder, sometimes along with vestigial manorial rights and tenures by grand serjeanty.