Windsor, William (c.1325–1384), Baron Windsor , lord lieutenant of Ireland, was the son of Sir Alexander Windsor of Grayrigg, Westmorland, and his wife, Elizabeth (d. 1349). He was a minor when his father died in 1343, but had attained his age of majority by 1349. He took part in the French wars of Edward III, and seems to have first served in Ireland in 1361 under Lionel, duke of Clarence (qv), lieutenant of Ireland; he was rewarded for this service with grants of land in Waterford and Cork. In March 1369 Windsor was appointed lieutenant of Ireland, with a personal grant of 1,000 marks, and arrived to take up his post on 20 June. Soon after his arrival he was active in Leinster, capturing the Leinster king, Diarmait Láimhdhearg MacMurrough (qv), and his tánaiste, Gerald MacMurrough: he executed them both later that year.
From his earliest days as lord lieutenant, Windsor was unpopular with some of the English nobility of Ireland for his attempts, as the king's representative, to increase the revenues of the government. On coming to Ireland he had been promised 20,000 marks over three years but the pressures of the renewed Anglo-French wars made it difficult for Edward III to provide on time the substantial sums of money Windsor had been assured of for the wages of his troops. Against this background Windsor made unprecedentedly frequent and heavy demands for taxation with predictable results. In August 1369 the Dublin parliament refused to promise any new customs to the king; Windsor then compelled the prelates to vote him a grant for three years, but recorded it in the chancery rolls as being in perpetuity. The outraged English of Ireland, encouraged by the earl of March (qv) (d. 1381), appealed to the king, but Windsor disregarded their protests and held another parliament at Dublin during April 1370 to raise more finance, increasing his unpopularity still further.
Windsor also set about settling the borders of the areas of English jurisdiction, marching against the O'Tooles of the Wicklow mountains in the early summer of 1370; but his attention was soon distracted from the Wicklow campaign by news from Munster of the defeat and capture of Gerald FitzGerald (qv), 3rd earl of Desmond, at Monasteranenagh (Limerick) on 11 July by Brian Sreamach O'Brien (qv) (d. 1399), king of Thomond. While Windsor was preoccupied with Brian Sreamach, the O'Byrnes (Uí Bhroin) seized Wicklow and Newcastle McKynegan castles in summer 1370, and, although these fortresses were quickly retaken, the O'Byrnes had already razed Wicklow. In Munster, Windsor first rescued the earl from the O'Briens (by 8 August), and then retreated to the earl's castle of Adare to plan how to retake the town of Limerick from the O'Briens and their MacNamara (Mac Conmara) allies. He sought to divide the O'Brien camp by patronising Brian Sreamhach's enemies, notably Murchadh na Raithnighe O'Brien (qv) (d. 1384); he also had considerable support from some MacNamara dissidents, the Burkes of Clanrickard, and the Berminghams. With their support, his troops retook Limerick, probably in late November 1370. On 15 December Windsor made a treaty with John MacNamara that confined his dynasty to the west side of the Shannon, ordering him not to interfere with the people of the town; he also required reparations of 1,000 fat cattle and 1,000 trees to aid in the repair of the town.
Windsor retired to Adare and held a parliament there on 8 January 1371, obtaining a grant of £3,000 for the government, which was conceded reluctantly. His enemies among the English of Ireland complained that he had not dealt firmly enough with the O'Briens and the MacNamaras in the aftermath of his victory over them, and also accused him of embezzling government funds. This active opposition led to a campaign seeking his return to England. One of his last acts on this first tour of duty in Ireland was to attempt to reach a settlement with the Irish of Wicklow: on 27 March he brought the O'Byrnes to peace, signing a treaty with Bran O'Byrne (qv) (d. 1378) in Christ Church cathedral, Dublin. The enemies of Windsor were triumphant when on 9 April 1371 he sailed for England, where his governorship was to be investigated. Within a week of his departure Brian Sreamhach and the MacNamaras had broken the peace and were plundering throughout Munster. On 10 September 1371 Edward III overruled Windsor's fiscal policies in Ireland and administered a formal rebuke to him on 20 October. It may have been at this time that Windsor married Alice Perrers (d. 1400), the former mistress of the king. By September 1373, however, an inquiry had cleared Windsor of all charges and it was clear that the king wanted him to return to Ireland; on 20 September he was reapppointed as chief governor of Ireland, though he was no longer allowed to use the exalted title of lieutenant.
After his return, Windsor sought to bring order to Munster in 1374, but his campaign lacked the success of that in 1370: Murchadh na Raithne O'Brien's power had increased greatly, making him less pliable, and Windsor's English forces were continually drained through desertion, forcing him to rely on Irish troops. At the same time the O'Byrnes abandoned their treaty with Windsor, capturing and demolishing Newcastle McKynegan, and burning Wicklow to the ground. Windsor had to be forbidden by the council at Naas to march against the O'Byrnes for fear that all Ulster would become unstable if the conflict escalated. By September Windsor's government had managed to establish a semblance of control over the Leinster coast, retaking Wicklow and Newcastle McKynegan.
Financial need led Windsor to hold three parliaments during 1375. On 17 January he obtained a grant for the maintenance of his retinue, while at Kilkenny on 16 June he extracted a grant of 4,000 marks from the clergy and commons of Munster, Kilkenny, and Wexford. From Kilkenny, he marched to Munster on 3 August to join Stephen de Valle, bishop of Meath, in a campaign against the O'Briens, but they fared poorly and the O'Briens sacked Adare. Windsor's position was further undermined when in July the king commissioned Nicholas Dagworth to go to Ireland on his behalf. On 6 October Dagworth addressed the Dublin parliament, requesting a royal subsidy, which was rejected on a plea of poverty; incensed, Dagworth produced letters under the privy seal, commanding the commons to elect representatives to travel to England before February 1376 to consult with the king. The same deadline was given to Windsor and several of his government, who were likewise summoned to appear before the king; however, it was June before Windsor finally vacated his high office in Ireland and sailed for England, a disappointed and angry man, caught up in the English political crisis.
On 16 August the mayor and the sheriffs of London were ordered to arrest Windsor, as he had quarrelled with some of his detractors in the king's presence at White Friars in Fleet Street. Two days later Windsor surrendered himself at the Tower of London to stand trial, but he was released on 20 August. His fortunes seem to have taken a turn for the better at this time, as on 12 September the county of York granted him £100 per annum. He was again entrusted with government office on 23 October 1379, when he was made keeper of the castle of Cherbourg. He resumed military service when he supported the duke of Brittany against the French. He received a personal summons to attend parliament as a baron in 1381 and in 1381–2 he played a leading role in suppressing the peasants’ revolt in Cambridge and Huntingdon, as well as serving as a special justice and commissary of the peace in Cambridge. Windsor died at Haversham, Westmorland, on 15 September 1384, heavily in debt to the crown that he had served so ably and faithfully.