[5][3] He received an official commission from the King on 10 December 1455 and also had been utilised by Henry to promote friendship between Lord Moleyns (his father-in-law) and one John Clopton.

[6] He was a staunch adherent of the House of York during the Wars of the Roses, and was knighted by King Edward IV at the Battle of Towton on 29 March 1461.

[a] In the same year he was appointed Constable of Norwich and Colchester castles, and became part of the royal household as one of the King's carvers, "the start of a service to the house of York which was to last for the rest of his life.

In 1467 he served as deputy for Norfolk as Earl Marshal at 'the most splendid tournament of the age' when Antoine, count of La Roche, the Bastard of Burgundy, jousted against the Queen's brother, Lord Scales.

By 1467 he was a Knight of the Body, and in September 1468 was appointed Treasurer of the Royal Household, an office which he held for only two years, until Edward lost the throne in 1470.

After 1463, he purchased a number of other manors, including six forfeited by John de Vere, 12th Earl of Oxford, the son of his cousin, Elizabeth Howard.

He was appointed Lord High Steward and bore the crown before Richard at his coronation, while his eldest son, the Earl of Surrey, carried the Sword of State.

With Catherine Moleyns, he had two sons and four daughters:[11][3] Howard married secondly, before 22 January 1467, Margaret (1436–1494), the daughter of Sir John Chedworth and his wife, Margaret Bowett,[b] and widow, firstly of Nicholas Wyfold (1420–1456), Lord Mayor of London, and secondly of Sir John Norreys (1400 – 1 September 1466), Master of the Wardrobe.

[15] By his second wife, Margaret Chedworth, he had one daughter:[15][3] As part of his duties as Earl Marshal, John Howard ordered the muster of lords, knights and common soldiers to the abbey at Bury St Edmunds to join Richard III to march on Redemoor Plain, better known as Bosworth Field.

He was slain at the Battle of Bosworth Field on 22 August 1485 by the knight Sir John Savage in single combat, according to the Ballad of Lady Bessy.

[20] He was buried in Thetford Priory, but his body seems to have been moved at the Reformation, possibly to the tomb of the 3rd Duke of Norfolk at Framlingham Church.