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
Within the members of each rank of the peerage, peers of England precede peers of Scotland. English and Scottish peers together precede peers of Great Britain. All of the aforementioned precede peers of Ireland created before 1801. Last come peers of Ireland created after 1801 and peers of the United Kingdom. Among peers of the same rank and Peerage, precedence is based on the creation of the title: those whose titles were created earlier precede those whose titles were created later. But in no case would a peer of a lower rank precede one of a higher rank. For example, the Duke of Fife, the last non-royal to be created a duke, would come before the Marquess of Winchester, though the latter's title was created earlier and is in a more senior peerage (the peerage of England).