Mowbray's father, the 2nd Baron, sided with Thomas, 2nd Earl of Lancaster, at the Battle of Boroughbridge on 16 March 1322 against Edward II, and was taken prisoner at the battle. He was hanged at York on 23 March 1322, and his estates forfeited. His wife and son John were imprisoned in the Tower of London until Edward II was deposed by his wife, Queen Isabella, and Roger Mortimer, 1st Earl of March. The Mowbrays were released in 1327. The 3rd Baron de Mowbray was reportedly in Edward III's good graces, being present in France in the War of the Breton Succession for the sieges of Nantes and Aguillon. He was also on the English side at the Battle of Neville's Cross in the Second War of Scottish Independence. He died of the plague at York on 4 October 1361, and was buried at the Friars Minor in Bedford.