[1] Born about 1360, he was the second son and heir of Sir Marmaduke Lumley (1314–1365), a landowner and administrator in Northumberland, and his second wife Margaret,[1] daughter of Robert Holland, 2nd Baron Holand.
In 1383 he received his inherited lands and had already embarked on a military career, being knighted and holding for ransom a number of French prisoners of war.
The next year he was summoned to Parliament as a baron and in 1385 was under the command of Henry Percy, 1st Earl of Northumberland, fighting the Scots in the defence of Berwick-upon-Tweed.
At the Battle of Otterburn in August 1388, he was taken prisoner by the Scots, not being freed until October 1389 after payment of a sizeable ransom, toward which both King Richard and the Bishop of Durham contributed.
All his moveable possessions were given to the king's half-brother John Beaufort, 1st Earl of Somerset, and his estates were forfeited to the crown, apart from lands yielding 100 pounds a year left to support his widow and twelve children.