He played a significant role in the wars in Scotland and Wales, and was appointed steward of the household to Edward II.

[2] In the same year he and his uncle, Amaury de St Amand, were imprisoned in the Tower of London for an alleged offence for which he was soon acquitted.

In February 1316 he played a leading part in suppressing a rebellion in Glamorgan by Llywelyn Bren (died 1318),[5][7] and, in July 1316, was sent to Bristol to settle grievances between the town's burgesses and Bartholomew de Badlesmere, 1st Baron Badlesmere (died 1322), Constable of Bristol Castle.

[7] However, on 20 November 1318, Edward II sent him to Gascony as Seneschal, [8] and he was replaced as Steward of the Household by Bartholomew de Badlesmere.

[5] According to Gross, "this was almost certainly a concession to Thomas of Lancaster, who had accused Montagu of combining with Roger Damory to plot against his life, a factor which delayed his reconciliation with the King".

[11][12][13] Elizabeth de Montfort survived her husband and remarried to Sir Thomas Furnivall (d. before 18 April 1332) of Sheffield, who was pardoned and fined £200 on 8 June 1322 for marrying her, a widow of a tenant-in-chief, without royal licence.