Sir William Parr (1434-1483) was originally a member of the Neville affinity, but switched sides during Warwick's second revolt against Edward IV and was rewarded richly for his decision.
Parr's father, Sir Thomas Parr of Kendal, was a member of the affinity of Richard Neville, earl of Salisbury. Salisbury was killed after the battle of Wakefield late in 1460 and Sir Thomas died in November 1461, and his son became a supporter of Salisbury's son Richard Neville, earl of Warwick. He was rewarded by Warwick, gaining several lucrative commissions in the north-west.
In 1469 Warwick turned against Edward IV. His plan was to use Robin of Redesdale's revolt to draw Edward north, then invade from Calais, trapping the king between the two armies. This plan worked. Edward moved north slowly, until he discovered that the rebel army was much larger than he had expected. He stopped then began a slow move south, hoping to join up with his allies William Herbert, earl of Pembroke and Humphrey Stafford, earl of Devon, who were raising an army in the south.
As Edward moved slowly towards Nottingham, Warwick reached London. He then sent a cavalry detachment north to find Redesdale's army. This force was commanded by Sir William Parr and Sir Geoffrey Gate, indicating that Parr was one of Warwick's most trusted men. On 24 July 1469 the rebels clashed with Pembroke's men at Edgcote (near Banbury). The battle fell into two parts, in both cases with the rebels attacking Pembroke's force. Devon played no part in the battle. The first attack was repulsed, but Parr and Gate then arrived with reinforcements and encouraged the rebels to attack again. This time they were victorious and Pembroke's force was scattered. Pembroke and his brother Sir Richard Herbert were both captured and beheaded. Devon escaped for the moment, but was killed in Somerset a few weeks later.
Warwick briefly had control of the kingdom, but found that he couldn’t rule without Edward. The king was released and soon regained his full power. He tried to rebuild a working relationship with Warwick, but early in 1470 the earl rebelled for a second time. This time he tried to take advantage of a revolt in Lincolnshire. Three armies were soon in the field - Edward heading north to deal with the rebels, Warwick and Clarence shadowing him a safe distance to the west and claiming still to be loyal and the rebels, under Sir Robert Welles, who at first heading south-west in an attempt to meet with Warwick. They then changed course in an attempt to save Welles' father Lord Welles, and suffered a heavy defeat at 'Losecote Field' (12 March 1470).
For the next few days Edward and Warwick continued to move north in parallel, exchanging messages as they went. Sir William was one of Warwick's messengers, and on 19 March he was sent to ask for a safe conduct and a pardon for his master and Clarence. Edward refused to take this dangerous step and instead demanded that Parr leave Warwick's allegiance and join with the king instead.
Parr must have followed Edward's orders and changed side. Warwick fled west to try and get help from Lord Stanley in Lancashire and when that failed escaped south to Dartmouth and then France. If Parr had stayed loyal to Warwick then he would either have fled or been imprisoned. Instead in May Edward appointed him lieutenant of Carlisle and the west march, and he wasn't listed amongst Warwick's supporters after the collapse of the revolt. Parr must have been horrified when Warwick successfully returned from exile later in 1470 and forced Edward to flee. He was removed as a commissioner of the peace for Cumberland and Westmorland and can only have expected worse in the future.
In March 1471 Edward IV returned from exile at the head of a tiny army. He managed to elude Warwick's men in the north, but failed to gain significant numbers of supporters until he reached the Midlands. The first sizable contingent to join him was 600 men from Lancashire led by Sir William Parr and Sir James Harrington. Edward went on to victory, defeated Warwick at Barnet (14 April 1471) and the Lancastrians at Tewkesbury (4 May 1471).
Parr had chosen the winning side, and he was now rewarded for it. He was made a knight of the king's body, was given Burgh, Pendragon and Appleby Castles and a third of the crown share in the barony of Kendal. He joined the royal council in July 1471 and was controller of the royal household from 1471-1475 and again from 1481. He served on embassies to Scotland and took part in the king's invasion of France in 1475. He was made a knight of garter in 1474. He also built up a close connection with Richard, duke of Gloucester, and was a member of his council.
In April 1483 he played an important role at the burial of Edward VI and he was also involved in the coronation of Richard III. We don’t know if he would have stayed loyal to Richard as his reign unfolded, for Parr was dead by 3 December 1483. His family survived the fall of Richard III and became prominent in the Tudor court. His most famous descendent was Katherine Parr, Henry VIII's sixth and final wife.