Both William and his brother were originally merchants in Ravenser; by the 1310s he had moved to
Kingston upon Hull. Both William and his brother Richard were already notable merchants by the late 1310s; by 1317 they were deputies of the
Royal Chief Butler, and from 1321 to 1324 both were chamberlains of the town. In the 1320s William was exporting increasing quantities of wool from Hull. During the same period William had begun providing finance to
Edward II relating to his conflict with the French over
Gascony; loans of £1,800 and £1,000 are recorded in 1325. The brothers had also become significant figures within the town of Hull; their actions included a sum of £306 spent on improving the
fortifications of Hull.After the downfall of Edward II, the brothers' importance within the state increased as a consequence of the resumption of the wars with Scotland in 1327 during the reign of
Edward III under the regency of
Roger Mortimer and
Queen Isabella; £4,000 was loaned for the Scottish campaign in 1327, in addition to £2,000 loaned for the pay of Dutch mercenaries employed during the ousting of Edward II. By 1329 the total loans exceeded £13,000, amounts comparable to those provided by the traditional royal financiers, the
Bardi of Florence. The De la Poles financed the loans through lending from other merchants. In return for these services the De la Poles obtained various privileges and other rewards from the crown. They obtained the manor of
Myton in 1330, and in 1332 William became the first
mayor of the town of Hull, a position he held until 1335; he also represented Hull in Parliament in several years of the 1330s. William and Richard de la Pole formally dissolved their partnership in 1331. William was increasingly in the service of the king during the 1330s, both acquiring supplies as well as providing ships for his wars with the Scots, and commissioning and commandeering ships for the dynastic dispute with France that became known as the
Hundred Years War. He jointly managed the
English Wool Company, set up by the king to finance his war through control of the wool trade. Smuggling of wool caused financial hardship and the collapse of the scheme. From June 1338 to October 1339 the king had to borrow over £100,000 from Pole; he acquired the estate of
Burstwick (or lordship of
Holderness) from the financially stricken king for £22,650, which brought about the king's resentment. In 1339 he settled a loan of 50,000 florins from the
Archbishop of Trier (Treves) in place of the king's crown, which had been used as collateral. The same year De la Pole achieved the rank of
Knight Banneret, and on 26 September 1339 he was made
Baron of the Exchequer. In 1340 William and Richard de la Pole, as well as
Sir John de Pulteney, were arrested. He was charged in relation to the failure of the English Wool Company, and De la Pole was incarcerated at
Devizes Castle and his lands seized; the charge was annulled in 1344. Between 1343 and 1345 he returned to organising the financing of the king's wars through the foundation of a new company. During a period of peace in the 1350s, the king renewed the wool smuggling charges against De la Pole, forcing him to renounce his claim to the manor of Burstwick; in 1354 he signed a document cancelling all the king's debts to him in exchange for his pardon.In 1350 he founded a hospital in Hull, named the
Maison Dieu; shortly before his death he obtained a licence from Edward III for the foundation of a religious house, originally intended to be of the
Order of Saint Clare. He died before it was completed, and the place was established by his son
Michael de la Pole, 1st Earl of Suffolk as a
Carthusian house dedicated to St. Michael (see
Charterhouse, Kingston upon Hull). ==Death and burial==