Born in Cassington, Oxfordshire, about 1302 Guillaume was the third Baron Montagu and the first Earl of Salisbury of the second creation. A leading diplomat and soldier under Edward III during the early stages of the Hundred Years War, he was made Marshal of England for life in 1338. He died in January 1344 of injuries received while jousting at Windsor and was buried in Bisham Priory, Maidenhead.
Family
He was the second, but first surviving son and heir of William, second Lord Montagu, by Elizabeth, daughter of Sir Piers de Montfort.
He was aged 17-18 in May 1320, having succeeded his father on 18 October 1319. In September 1325 he was going overseas with the King, being then presumably the King's yeoman. Knighted in 1326 he was summoned for service in Scotland 1327. In May 1329 he attended the King to do homage at Amiens, and in June began his successful service as a diplomatist.
In July following he had a grant in consideration of labours daily endured by him, dwelling at the King's side. He was prime mover in the seizure of Mortimer in 1330, and was summoned to Parliament as Lord Montagu on 18 February 1331. In April 1331 he accompanied the King on his short secret journey to France. In September he held a great tournament in Chepe.
One of the keepers of Somerset in 1332, and later commissioner of the peace. In that year he became lord of Lundy Island by purchase. In 1333 he was in command of the siege of Berwick.
Warden of the Isles
From March 1334 to May 1337 he was joint Warden, with Henry de Ferriers, of the Channel Islands.
- R commisit Willelmo de Monte acuto et Henr de Ferrariis custodiam insularum R de Gerneseye, Jereseye, Serk et Aureneye et aliarum insularum eisdem insulis adjacencium, habendam et regendam una cum omnibus, proficuis etc Usque ad finem quinque annorum, reddendo inde Regi per annum quingentas marcas, ita quod iidem Will. et Henr. castra R. etc sustentent etc
In 1335 the two Wardens were replaced in the islands by a lieutenant, whose name is not known. On 3 October 1336 they had Gautier de Weston, later a Warden in his own right, as lieutenant, and with him they were entrusted, for a year, with the mandate of receiving in the name of the King, the hommage he was due in the islands.
Marriage
He married, in or before 1327, Katharine, youngest of the three daughters of William Grandison, a formerWarden of the Isles and niece of Lord of the Isles Otto de Grandison.
They had five children, Elizabeth; William, his heir; Sibyl, John and Phillipa.
Descendants
There are some fascinating lines of descent from Guillaume.
One line can be traced to the Pauletts, who were Governors and Bailiffs of Jersey in the 16th Century, and married into the de Carteret family; and another to Richard Neville Lord of the Isles and his wife Anne de Beauchamp the only woman to have been her monarch's representative in the Channel Islands. A third line goes direct to King Edward IV, Henry VI and Henry VII and subsequent monarchs.
Family tree
Descendants of Guillaume de Montagu
| Predecessor | Successor | |
| Thomas Wake of Liddell 1331-1333 |
Guillaume de Montagu and Henry de Ferriers 1334 - 1337 |
Thomas de Ferrers 1337 – 1341, 1343 - 1347 |
