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).
List of viscountcies in the peerages of Britain and Ireland
Viscounts were created in the peerages of England and Scotland until the Act of Union 1707, thereafter being created in the peerage of Great Britain. After the Acts of Union 1800 came into effect in 1801, all peerages were created in the Peerage of the United Kingdom. Viscounts in the Peerage of Ireland were created by English and British monarchs in their capacity as Lord or King of Ireland. Irish peers were not initially granted a seat in the House of Lords and so allowed the grantee to sit in the House of Commons. Viscounts of Ireland have precedence below peers of England, Scotland, and Great Britain of the same rank, and above peers of the United Kingdom of the same rank; but Irish peers created after 1801 yield to United Kingdom peers of earlier creation.