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
The next major event in the history of the Peerage occurred in 1707, when England and Scotland united into Great Britain. There were, at the time, one hundred and sixty-eight English peers and one hundred and fifty-four Scottish ones. English peers did not wish for their individual significance in the House of Lords to dwindle, so they agreed to permit Scotland to elect just sixteen representative peers to sit in the House of Lords (see Parliament and the Peerage). After the Union, creations in both the Peerage of England and the Peerage of Scotland ceased and all new peerages were created in the Peerage of Great Britain.