Dictionary of National Biography, 1885-1900/Mohun, William de (fl.1141)
MOHUN, MOION, or MOYNE, WILLIAM de, Earl of Somerset or Dorset (fl. 1141), eldest son of William de Mohun (fl. 1066) [q. v.], by his wife Adelisa, was possessed of forty-four knights' fees, and in 1131 was present at the council held by Henry I at Northampton, and one of the witnesses of the charter there granted by the king to the church of Salisbury. He rose against Stephen in 1138, and, relying on the strength of his castle of Dunster, committed many deeds of violence and cruelty in the west country. Stephen marched against him, but believing Dunster Castle to be impregnable, and being unwilling to remain long enough before it to compel its surrender by blockade, marched away, leaving Henry Tracy to carry on the war in those parts. This Tracy did with success, preventing William from continuing his expeditions from Dunster, and on one occasion taking 104 knights prisoners. William was humbled and compelled to remain quiet (Gesta Stephani, pp. 52, 53). He was with the empress at Westminster in June 1141, and marched with her to the siege of Winchester. There it is said (ib. p. 81) that the empress made him Earl of Dorset, but it appears that he was an earl when he was at Westminster in June (Round, Geoffrey de Mandeville, p. 93). He called himself Earl of Somerset (Monasticon, vi. 335), but the close connection then existing between the two shires renders this apparent discrepancy of no importance. In 1142 he founded a priory at Bruton for Augustinian canons. He also granted land to the monks of Dunster to pray for the soul of his son Ralph (Lyte, p. 28). By his wife Agnes he had six sons, of whom four were clerks, and another, Ralph, predeceased him. A son William succeeded him, but did not, as far as is known, bear the title of earl, and was in turn succeeded by his son Reginald de Mohun, father of Reginald de Mohun (d. 1257) [q. v.]
[Lyte's Dunster and its Lords, pp. 5, 6, 28; Gesta Stephani, pp. 52, 53, 81 (Engl. Hist. Soc.); Ann. Wav. ap. Ann. Monastici, ii. 226 (Rolls Ser.); Sarum Charters, p. 7 (Rolls Ser.); Liber Niger Scacc. i. 91, ed. Hearne; Dugdale's Monasticon, vi. 335; Dugdale's Baronage, i. 497; Round's Geoffrey de Mandeville, pp. 93, 95, 125, 271, 277; Stubbs's Const. Hist. i. 362, 451; Somerset Archseol. Soc.'s Proc. 1857 vn. ii. 73-75, 1873 xix. ii. 96.]