Dukes in the United Kingdom
Duke, in the United Kingdom, is the highest-ranking hereditary title in all four peerages of the British Isles. A duke thus outranks all other holders of titles of nobility (marquess, earl, viscount and baron).
Baron de Ros
Baron de Ros (pronounced "Roose") is the premier baron in the Peerage of England, created in 1288/89 for William de Ros, with precedence to 24 December 1264. (The spelling of the title and of the surname of the original holders has been rendered differently in various texts. The word "Ros" is sometimes spelt "Roos", and the word "de" is sometimes dropped.) "Premier baron" is a designation and status awarded to the holder of the most ancient extant barony of the Peerage of England. The present premier baron is Baron de Ros. Before the Dissolution of the Monasteries the Prior of the Order of St John in England was deemed premier baron.