William inherited the manor of Harringworth, including a park and wood, upon the death of his mother Millicent de Cantilupe in 1299.

[7][non-primary source needed] In February 1322, William was ordered to muster as many men-at-arms and foot soldiers as he could and to march to the King to aid in the suppression of the rebels of Thomas, 2nd Earl of Lancaster.

[7][non-primary source needed] He was summoned to defend Aquitaine in 1324, which was lost under the poor leadership of Hugh le Despenser, 1st Earl of Winchester, and to go to Gascony in 1325.

[7][non-primary source needed] After Queen Isabella and Roger Mortimer, 1st Earl of March's successful overthrow of her husband, Edward II, William was summoned to the Parliament held in January 1327[7][non-primary source needed] which decided it had lost confidence in the rule of Edward and forced his abdication.

Inquisition post mortems found he held land in Shropshire, Wiltshire, Norfolk, Bedfordshire, Buckinghamshire, Rutland, Warwickshire, Leicestershire, Lincolnshire, Northamptonshire and Worcestershire.