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).
History of the British peerage
During the reign of Henry VIII, peers attempted to consolidate and secure their position. They declared themselves "ennobled in blood," and suggested that no peerage could be extinguished except by an Act of Parliament, upon the extinction of all heirs to it, or upon forfeiture for treason or felony. The Spiritual Lords had attempted to secure the privileges of the Peerage while maintaining their ecclesiastical privileges, but lost in both attempts. Nonetheless, they were in the majority in the House of Lords until the Dissolution of the Monasteries, which removed the abbots and priors from the House. Thereafter, the temporal peers formed for the first time a majority in the Lords.