William de Grandison (younger brother of Sir Otho de Grandison, secretary to King Edward I, and afterwards Lord Grandison), being originally a menial servant to Edmund, Earl of Lancaster, obtained from that prince, in consideration of his own faithful services and the services of his ancestors, a grant of the manors of Radley and Menstreworth, co. Gloucester. In the 20th Edward I [1292], he procured license to make a castle of his house at Asperton, co. Hereford, and in two years afterwards he was in the expedition made into Gascony, where he continued for some time and, while so engaged, was summoned to parliament as a baron. He was afterwards engaged in the Scottish wars.
His lordship m. Sibilla, youngest dau. and fo-heiress of Sir John de Tregoz, and upon partition of the lands of that inheritance, acquired the manors of Burnham, co. Somerset, and Eton, in Herefordshire. He had issue by this lady, viz., Peter, John, Otho, Mabella, Katherine, and Agnes. His lordship d. before 1335 and was s. by his eldest son, Peter de Grandison, 2nd baron. [Sir Bernard Burke, Dormant, Abeyant, Forfeited, and Extinct Peerages, Burke's Peerage, Ltd., London, 1883, p. 242, Grandison, Barons Grandison]