[2] In 1307, he was at the head of an English force of 1,000 men going from Bothwell Castle to Kyle when they were ambushed by Bruce's ally Sir James Douglas.
While his forces retreated to Bothwell, Mowbray, who had lost his sword, fled a long way to Inverkip Castle.
[3][4] According to John Barbour's The Brus: Sync throu the Largis, him allane Till Ennerkip the way he tane, Rigcht to the castell that wes then Stuffyt all with Ingless men,
It came under prolonged siege from Edward Bruce, the King's younger brother, and in 1314 they made a deal that the castle would return to Scottish control unless relieved by English forces before 24 June.
His daughter Phillippa married Bartholomew de Leon, she was restored her brother's forfeited lands in 1346, their son David adopted the names and arms of Mowbray.