 William was sheriff of Forfar (1195–1211), Justiciar of Scotia (1205–1233) and warden of Moray (1211–2).Between 1199 and 1200, William was sent to England to discuss important matters on King William's behalf with the new king, John.William was appointed to the prestigious office of Justiciar of Scotia, the most senior royal office in the kingdom, in 1205.