From his actions it can be assumed that Wrotham was a member of the royal household, probably working in the wardrobe. William's main administrative work concerned the navy. In 1204 he, de Cornhill, and William of Furnell were placed in charge of granting wool export licences. William of Wrotham was also one of the officials charged with supervising the ships dispatched to the coasts in 1204, after the loss of Normandy exposed England to invasion by the French. In 1205 he was again one of the keepers of the royal fleet along the south coast. William was in charge of the 17 ships based in Romney, Rye, Shoreham, Southampton, Winchelsea, and Exeter, while the rest of the fleet came under Cornhill's control. In the same year, he was also in charge of naval spending for the attempted invasion of France, which in June alone totalled over 470 pounds. William surrendered custody of Taunton Castle to Peter de Taraton in July and was in charge of purchasing the royal wine in August. No further naval duties are recorded until November, when along with Cornhill he was responsible for assessing the ports. In 1206 William was in charge of the naval forces in the Cinque Ports and commanded the fleet that invaded Poitou. Whether he accompanied the fleet or stayed in England after it sailed is unclear; according to two historians – F. W. Brooks and R. W. Powell – it is more likely he stayed. From 1206 until 1215 he was effectively commander of King John's navy, and helped to develop Portsmouth as a royal dockyard. In 1208 William was put in charge of ensuring that no ships sailed without royal permission. That year he also oversaw the naval preparations made by the Cinque Ports. The purpose of these preparations is unknown; the "Annals of Dunstable" ascribe to John a desire to oppress the Cinque Ports. During May 1208 a royal order was issued that William's deputies in all the seaports should seize any ships in the ports that were from foreign countries, excluding Denmark, Norway and other countries that did not oppose John's diplomatic efforts. A gap in the governmental records does not allow a detailed view of William's activities for the next years, until 1212, when William is shown performing many of the same duties as earlier. He was in charge of repair of some ships and the construction of a large new ship, named the "Deulabenit", owned by the king.