The creation and appointment of the Lord Warden, once among the most powerful appointments of the realm, by the Sovereign was instituted principally after the portsmen sided with the Earl of Leicester against King Henry III, in the Second Barons' War, and was intended to provide some central authority over the Cinque Ports, which were essentially otherwise independent of the King's sheriffs. It was combined from 1267 with the office of Constable of Dover Castle. However, from 1708 Walmer Castle at Deal was to be preferred as the official residence of the Lord Warden of the Cinque Ports. The Lord Warden also holds the office of Admiral of the Cinque Ports with a maritime jurisdiction extending to the middle of the English Channel, from Redcliffe near Seaford, in Sussex to the shore underneath the Naze Tower, encompassing Brightlingsea in Essex, the only Cinque Port north of the Thames. In earlier centuries the northern limit was taken as the Shoe Beacon in Essex.