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).
Robes of the British peerage
For male peers, the Coronation robe is a cloak of crimson velvet extending to the feet, open in the front (with white silk satin ribbon ties) and trailing behind. Attached to the robe is a cape and collar of miniver pure; the rank of the peer is indicated by rows of "ermine tails (or the like)" on the miniver cape: 4 for a duke, 3½ for a marquess, 3 for an earl, 2½ for a viscount and 2 for a baron. (Royal dukes have six rows of ermine, and additional rows on the collar and on the front edges of the garment.) Peers are entitled to wear the coronation robe whether or not they are members of the House of Lords.