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).
Peerage of Ireland
The last two grants of Irish peerages were: the promotion of the Marquess of Abercorn (a peerage of Great Britain) to be Duke of Abercorn in the Irish Peerage when he became Lord-Lieutenant of Ireland in 1868 and the granting of the Curzon of Kedleston barony to George Curzon when he became Viceroy of India in 1898. Peers 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. Accordingly, the Duke of Abercorn (the junior Duke in the Peerage of Ireland) ranks between the Duke of Sutherland and the Duke of Westminster (both dukes in the Peerage of the United Kingdom).