The subsidiary titles of the Duke of Northumberland are: '' Earl Of Northumberland '' (created 1749 ), ''Earl Percy'' (1766), ''Earl of Beverley'' ( 1790 ), ''Baron Warkworth'' (1749) and ''Baron Lovaine of Alnwick'' ( 1784 ). All titles are in the Peerage Of Great Britain . The Courtesy Title of the eldest son and heir to the Duke is ''Earl Percy''.
