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.
Peerage law
For the early part of English history, peers sometimes surrendered their peerages to the Crown. Most surrenders occurred during the early years of the nation, but surrender occurred as late as 1640, when Roger Stafford, 6th Baron Stafford was ordered to surrender his dignity to the Crown in return for eight hundred pounds sterling. Later that year, however, the House of Lords, in order to guard the position of its members, which had been threatened by the power to order surrenders of peerages, resolved, "(i) That no person that hath any Honour of him and a Peer of this Realm, may alien or transfer the Honour to any other Person, (ii) That no Peer of this Realm can drown or extinguish his Honour, but that it descends to his descendants, neither by Surrender, Grant, Fine, nor any other conveyance to the King."