Wingfield’s father, Richard, a cadet of the important family seated at Wingfield in Suffolk, held the manor of Dennington and died shortly before 1349, when it was William who acted as patron of the local church. The latter was subsequently also possessed of manors in Cotton and Stradbroke as well as substantial holdings at Newton Gipping, Mendlesham, Finningham and Bacton, all of which were situated in the same part of the county. He extended his territorial interests into Norfolk by his purchase, in 1385, of ‘Botourys’ in Kymberle,
It is generally accepted that William was a first cousin of Sir John Wingfield (d.1361) of Wingfield and of Sir John’s brother, Thomas (d.1378) of Letheringham.
After the death of his cousin Sir John Wingfield, William left Prince Edward’s company to become a favoured retainer of Thomas de Vere, earl of Oxford. In December 1364 de Vere obtained a royal licence to grant to his esquire for life the manors of Langley and Bradley in Berkshire, and he subsequently also gave him and his first wife a joint life estate in the manors of Market Overton and Paston in Northamptonshire. These properties provided Wingfield with an annual income of as much as £35. In addition, de Vere bestowed on his retainer for life the sinecure keepership of Camps park (Cambridgeshire), a post which entitled him to a regular supply of grain, fodder and horseshoes. It was while in Earl Thomas’s service that Wingfield was made a knight, and he followed him across to France in the duke of Lancaster’s army in 1369, there to take part in the engagement ‘a le Hille vers Harreflete’ (Harfleur). Their relationship clearly continued to be a close one: the earl employed Wingfield as a feoffee-to-uses for the settlement of jointure on his wife Countess Maud, and Sir William made his lord a present of a coat of mail, which the earl treasured sufficiently highly to bequeath to his brother, Sir Aubrey de Vere. Another of the bequests in the earl’s will, made in 1371, favoured Wingfield’s wife. In December that year, after Thomas de Vere’s death, the widowed countess, feeling too weak to travel, named Sir William as one of her attorneys to sue in Chancery for her dower lands.
Wingfield was returned to his first Parliament in 1376 in the company of Sir Richard Waldegrave. This was the first instance of combined service on the part of these two shire knights, who were to form a unique pair as representatives for Suffolk, for they sat together in no fewer than nine Parliaments. Their earliest recorded association had occurred 11 years earlier when Wingfield, acting as a feoffee of the estates of the late Sir Robert Bures, had conveyed to Waldegrave and his wife Joan, Bures’s widow, her dower portion from the same. But it seems to have been their parliamentary experience in each other’s company which laid the foundation of their friendship: when in London to attend the Commons they sometimes lodged at the same hostel; they named each other as trustees; and at the end Wingfield was to ask Waldegrave to act as an executor of his will. In this Parliament of 1376, known at the time as the Good Parliament, Sir William played a prominent part in the Commons’ attack on ministerial corruption, by providing evidence for the impeachment of John, Lord Neville of Raby. His sympathies may have been determined by his early connexion with the Black Prince, who seems to have supported the stand taken by the shire knights; certainly he had maintained a close association with some of the prince’s retainers. For instance, in the previous year he had acted as a trustee of the manors in East Anglia belonging to Sir Thomas Felton, the seneschal of Aquitaine and former steward of Prince Edward’s household, and he was later to serve in a similar capacity on behalf of Felton’s widow.
Before his first return to Parliament Wingfield had been appointed to a few royal commissions; following it, he was to be kept almost constantly employed in the business of local government in East Anglia, and from 1378 until shortly before his death 20 years later he was to be a member of the Suffolk bench. All this administrative activity happened despite the fact that during his second Parliament, in October 1378, he obtained letters patent of exemption from being put on assizes or holding any office by crown appointment against his will. Few rewards ever came his way: there was merely a short lease granted at the Exchequer in June 1378 of rents pertaining to the manor of Thorp by Hadesco (Norfolk), and the wardship and marriage of the heir of a minor landowner. In February 1382, while attending the second session of the Parliament of 1381, he and John of Gaunt’s retainer, Sir Henry Green, shared a grant from the duke of the farm of the manor of Willisham (Suffolk), rent-free for the duration of a minority. As there is no other evidence to connect Wingfield with Lancaster in a personal way, it may be the case that this favour marks an attempt by the duke to attach the shire knight to his interests of the moment, for he needed support in the Commons for his Castilian venture.
Well-respected in the community of East Anglia, Wingfield was constantly in demand as a trustee of estates and an executor of wills. In the 1360s he had been a feoffee-to-uses of the important Bures estates inherited by Sir Richard Waldegrave’s stepdaughter, Alice; the early 1370s saw him taking on the trusteeship of those of John, Lord Bourgchier, as such exercising Bourgchier’s rights of presentation to the hospital of St. Giles at Little Maldon (Essex); and in 1375 he had served as executor of the will of the Norfolk landowner, Sir Ralph Shelton the elder. Along with Waldegrave, he became in 1377 a custodian of yearly rents amounting to £300 from manors in Nottinghamshire and Yorkshire, in this instance on behalf of Waldegrave’s kinsman, Sir John Burgh. More significantly, he had attracted the attention of William Ufford, earl of Suffolk (d.1382), who thought so highly of him as to leave him in his will, made in June 1381, an ‘enpension’ of £20 a year for life as well as a covered goblet to keep in his memory. In later years Wingfield served as a feoffee of the estates of the earl’s kinsman, Sir Robert Ufford. Then, in 1384-5, he was involved in property transactions on behalf of John Bacon, the King’s secretary, a connexion which had probably come about through the intervention of his kinsman by marriage, Michael, Lord de la Pole, who was then chancellor and shortly to be created earl of Suffolk.
Wingfield was a Member of the Commons in 1386 when his kinsman and friend, Michael, earl of Suffolk, was impeached. Whether or not he openly expressed his opposition to this, Suffolk’s enemies saw no reason to dispense with his useful services in the sphere of local government, and throughout the period of their rule he continued to be placed on royal commissions. Furthermore, even though he was not elected to the Merciless Parliament, in which de la Pole was condemned for treason, it was he, and not either of the Suffolk representatives, who was assigned the task of administering among the gentry of the shire the oath of loyalty in support of the Lords Appellant. It may be that these Lords believed him to be sympathetic to their policies; indeed, an inclination towards the Appellants provides a reason for Wingfield’s omission from the list of j.p.s appointed in July 1389, shortly after Richard II had re-asserted his personal authority. Yet Sir William was so invaluable for the effective government of Suffolk that it was only a few months before he was restored to the bench. He was returned to Parliament for the last time in November 1390; and during the session he and his fellow shire knight, Sir William Burgate, stood bail for the release from the Tower of John Rokele of Essex, guaranteeing that he would appear before the assembly on charges brought by the abbot of St. Osyth. The fortunes of the de la Pole family had suffered a serious rebuff in 1388, and the earl of Suffolk had died in exile in the following year. But Wingfield continued to offer support to the earl’s son, Sir Michael de la Pole, the new owner of the main Wingfield estates: he witnessed deeds on Sir Michael’s behalf in 1392 and 1397; and in the meantime he became a feoffee of his lands and, in October 1396, stood as godfather at the baptism of his second son, William (who was eventually to be the 4th earl of Suffolk).
There is no evidence that Wingfield was of an unusually pious disposition, although he had made grants in mortmain in 1382 to the chantry at St. Mary’s altar in Dennington church, and in 1390 to the minoresses of Bruisyard.