Sir Henry de Grey saw military service under Edward I, was summoned to Parliament by writ in 1299, and before that on the Gascony campaign of 1294–1297. He campaigned with Edward I at the Siege of Caerlaverock, and may have been with him on his last and fatal campaign across the Solway Firth in 1306–07. He seems to have been summoned to the Model Parliament as one of the King's great nobles. His first wife was Eleanor Courtenay, sister of the 1st Earl of Devon, a fellow officer. After her death he married Joan, daughter of Sir Ralph de Cromwell by 6 June 1301. He only left three children before he died in September 1308. His eldest, Sir Richard (1282–1335) was one of the Lords ordainer who rebelled against the Despencers, favourites of Edward II, but was subsequently pardoned in 1321. His son, Sir John took his mother's FitzPayne lands in Nottingham, distinguished himself on the battlefield in Scotland and was appointed a Knight of the Garter. Lord Grey was at the Battle of Crecy and Siege of Calais. He was appointed Keeper of Rochester Castle, and married Alice, daughter of Sir Warren de Lisle, himself a distinguished soldier. His son, Sir Henry married the daughter of one of the most distinguished generals of Edward III's court, Sir Reynold de Cobham KG, a brilliant commander, victorious in many battles and ancestor of the Viscounts Cobham. Grey married Joan de Cobham who gave birth to Richard, 1st Baron Grey de Codnor.