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).
Peerages in the United Kingdom
Some peers, particularly life peers who were well known before their ennoblement, do not use their peerage titles. Others use a combination: for example, the author John Julius Norwich was John Julius Cooper, 2nd Viscount Norwich.