Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. Sir John Grey KG (c. 1387 August 27, 1439), English nobleman and soldier, was the eldest son of Reginald Grey, 3rd Baron Grey de Ruthyn and Margaret Roos. He fought at the Battle of Agincourt, and was Lord Deputy of Ireland 1427 1428. He was invested as a Knight of the Garter in 1436. He married Constance Holland (1387 1437). She was the daughter of Elizabeth Plantagenet, (also known as Elizabeth of Lancaster), and John Holland, 1st Duke of Exeter, the half brother of King Richard II. She was also a niece of King Henry IV. She was first betrothed to Thomas Mowbray, 4th Earl of Norfolk as a 4-year-old child, but the marriage was never consummated, due to his early death as punishment for a revolt against her uncle, King Henry IV.