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
The ranks of baron and earl date to feudal, and perhaps Anglo-Saxon, times. The ranks of duke and marquess were introduced in the 14th century, and that of viscount in the 15th century. While peerages for life were often created in the early days of the peerage, their regular creation was not provided for by Act of Parliament until the Appellate Jurisdiction Act 1876.