The 'battle' of Heworth (24 August 1453) was a skirmish between the Neville and Percy families that raised tension in the north of England in the period immediately before the outbreak of the Wars of the Roses
The Nevilles and the Percies had been rivals in the north of England since the late fourteenth century, when Ralph Neville, earl of Westmorland (1354-1425), made his family into a power to rival the Percy earls of Northumberland. The Percy family fortunes plummeted during the reign of Henry IV when Henry Percy, first earl of Northumberland, and his more famous son Henry Percy 'Hotspur', rebelled against the king and lost. Hotspur was killed at the battle of Shrewsbury in 1403, his father's estates were forfeited after another revolt in 1405 and the earl was killed at the battle of Bramham Moor in 1408. Their lands were distributed to various supporters of Henry IV.
Despite this setback the family survived. Hotspur's son, another Henry, had escaped into exile in Scotland. After the death of Henry IV he was reconciled with Henry V and in 1416 he was created second earl of Northumberland. The restored earl managed to recover most of his family's original lands, but some remained out of his hands.
While the Percies were struggling the Nevilles remained in favour, but they developed an internal family feud between the children of Ralph Neville's first wife, who inherited the title earl of Westmorland, and the children of his second wife, who inherited most of the land (this branch was led by Richard Neville, earl of Salisbury). By the early 1450s a feud had developed between the Percies and Salisbury, which would end with them fighting on opposite sides during the Wars of the Roses.
In 1453 Sir Thomas Neville, Salisbury's second son, married Maud Stanhope, Lady Willoughby. She was the niece and heir of Ralph Cromwell, Lord Cromwell, who at this point held the former Percy manors of Wressle in Yorkshire and Burwell in Lincolnshire. This marriage meant that a Neville would probably inherit these former Percy lands, and that was something that Thomas Percy, Lord Egremont, apparently found unacceptable.
Egremont gathered together a force of at least 710 Percy supporters (in June 1454 the Nevilles began legal proceedings against 710 named members of Egremont's force, so the actual number present was almost certainly higher). This force included many men from Yorkshire, but also a contingent from Cockermouth in Cumberland, so the attack had obviously been well planned. Egremont was also supported by his brother Richard Percy, and John Clifford, later Lord Clifford.
The marriage party was also sizable. It was led by Richard Neville, earl of Salisbury. His wife was present, along with the married couple and another of Salisbury's sons, John Neville. They were travelling with a large number of their retainers.
The two sides clashed at Heworth Moor, then just to the north-east of York, and now part of the city. The Nevilles were able to force their way through the Percies, and reached their original destination at Sheriff Hutton. The amount of actual fighting involved is unclear as is the number of casualties (if any).
In the aftermath of this clash the Percies continued to attack Neville estates across the north. Salisbury attempted to get satisfaction at court, but Henry VI was either unwilling or unable to intervene satisfactorily. The tension continued to rise in the north. The two sides nearly clashed in October 1453, and the feud became a major issue during Richard, duke of York's period as Lord Protector in 1454. York's attempts to punish Egremont helped convince Salisbury to support him when civil war broke out in the following year. Armed conflict broke out in the north in 1453, and Egremont was captured at the battle of Stamford Bridge (31 October or 1 November 1454). He spent the next two years in debtor's prison before escaping to become a prominent supporter of Henry VI.