Why William de Leybourne is called the first English admiral

William de Leybourne served Edward I and Edward II, although both the spelling of his name and the date of his admiralty appointment remain uncertain. Surviving titles include captain of the kingdom's sailors and mariners, admiral of the English seas, admiral of the south and west, and admiral of the Irish Sea. His authority covered the forces used for royal naval operations, but the office was based mainly ashore and concerned administration, supplies, and making sure a navy could go to sea. Sir Gervase Alard received the first explicitly seagoing appointment under de Leybourne in 1303 as Admiral of the Cinque Ports. That division makes de Leybourne look more like a medieval precursor to the First Sea Lord than a modern fleet commander.