William Mountfort’s grandfather, John, was one of two illegitimate sons of Peter, 3rd Lord Montford (d.c.1369) of Beaudesert, through whose generosity he inherited the manors of Remenham (Berkshire) and Monkspath, Ilmington and Ullenhall in Warwickshire, although the principal Montfort estates passed to the descendants of Lord Montfort’s legitimate daughter, namely, Sir Baldwin Freville and Sir Thomas Butler of Sudeley. Coleshill itself, a village near Maxstoke castle, was acquired through the grandfather’s marriage to an heiress. When William’s father, Sir Baldwin, died in Spain in 1386, his heir was his elder son, John, who by grant of his maternal grandfather, Lord Clinton, was placed in the wardship of the influential Sir William Bagot; but John died in about 1394 and after a short spell as Bagot’s ward William himself became ‘lord of Coleshill’.
By 1417, Mountfort could reckon on receiving a clear annual income from his estates of over 455 marks (£304); and he then calculated that in the event of his death the profits for nine years would provide his eldest son, Baldwin, with 100 marks a year, his five other sons with flat sums of 400 marks each, his two daughters with 500 marks each, and his retainers with 200 marks to be shared between them. Clearly, the assessments of 1436 which accounted him the wealthiest non-baronial landowner in Warwickshire with an income of £281 p.a. (including that from property already settled on his eldest son), undervalued his worth.
Mountfort’s wealth, together with the geographical importance of Coleshill, situated where the principal roads of north Warwickshire met, soon made him an important local figure; and his early associates included Thomas Raleigh (who like himself had recently inherited substantial estates), and the latter’s father-in-law, Lord Astley, and kinsman by marriage, Lord Willoughby. But the years after he attained his majority saw him often in trouble: in 1396 he was to be arrested and brought before the King’s Council; two years later he was associated with Sir Adam Peshale in an unsavoury affair which involved making a prisoner sign bonds under duress; and in 1406 he killed an esquire (though he managed to obtain a royal pardon). At the time of his first return to Parliament in 1410 he was engaged in lawsuits with Sir John Eylesford. He is not actually known to have been elected to Parliament under Henry V, but he at least attended the Warwickshire elections to the first Parliament of the reign, that of May 1413, there standing surety for John Mallory.
In the meantime Mountfort had formed a strong attachment to Richard, earl of Warwick, becoming one of his most important retainers. Their families had long been connected, for Mountfort’s mother, being a daughter of Lord Clinton, was a descendant of the famous Earl Guy. By November 1410 Mountfort had established links with the Warwick retainers Robert Hugford and Thomas Gower (both of whom he named as trustees to affect an entail of the Pecche estates), and in July 1415 he took out royal letters of protection to cross to France in the earl’s retinue. At Easter 1417 he was made a feoffee for the settlement of the manor of Baginton on Warwick, and at the same time he asked the earl to reciprocate by taking on the trusteeship of his own estates. He was then making preparations to return to France in Warwick’s company; he was mustered under his colours at Southampton in the summer and, while abroad, acted not only as steward of his household but also as his lieutenant at Aumâle. After Mountfort was knighted he received a high retaining fee of 40 marks a year from Earl Richard, and was evidently regarded as an important member of his council while they were overseas. He was probably with Warwick throughout the conquest of Normandy, although in March 1420 he is known to have been seconded to the garrison at Falaise, under the command of Lord Fitzhugh. Having returned to England early in 1421, when Warwick accompanied the King home, he was a member of the earl’s entourage for his visit to Berkeley castle that March. Mountfort made preparations to return to France in July following, but probably came back early in 1422, for it was then that he was appointed to the Warwickshire bench. As a Member of the Commons in the first Parliament to meet after Henry V’s death, he no doubt helped to represent the Beauchamp interest.
Meanwhile, in one of the early Parliaments of Henry VI’s reign (possibly that of 1423), Mountfort had successfully petitioned for letters of denization to be granted to his second wife, Joan, who had been born in Brittany (which letters, however, she did not trouble to take out until after his death). In April 1430, as a ‘King’s knight’, he indented to serve in France for a year with his own company of 40 men, thereby adding to the already substantial army which Warwick, the King’s ‘governor’, deemed necessary to escort Henry on his journey to Paris for his coronation. Sir William returned home to be appointed sheriff for the first of three terms in 1431, and as such he held parliamentary elections in 1432. For a while he was seemingly preoccupied with local affairs: in 1434 he was among the gentry of Warwickshire required to take the general oath against maintenance, and in the following year, as a j.p., he heard the initial indictments against nine Oxford scholars who had allegedly ambushed and tried to kill him. (The case was deferred to the King’s bench.) But events in France still retained his interest: in 1436 he contributed separate loans of £40 and 100 marks for the duke of York’s expedition, and in the summer of 1437, when Warwick was appointed lieutenant of France and Normandy, he himself again took up arms. Under the earl’s command he held office as captain of Honfleur, though he was absent from the garrison in April and June 1438 on visits to Rouen for consultation with him. In December 1439, after Warwick’s death, Mountfort was included in a committee of trustees, named by the widowed countess, Isabel, who were granted custody of the Beauchamp estates during the minority of the heir, Henry. The countess also asked him to be an executor of her will. It was by appointment of the young earl’s guardians that he was again made deputy sheriff of Worcestershire in the following year.
After the death of Earl Richard, Mountfort drew closer to the Court: it was again as a ‘King’s knight’ that in 1443 he obtained exemption from holding office against his will, and shortly afterwards his favourite son, Edmund (who had been with him at Honfleur), became a member of the royal household, quickly rising to the post of carver to Henry VI. Mountfort’s friends during this period included the former Beauchamp retainer (Sir) William Peyto of Chesterton, who looked to him for help when trying to raise money for his ransom after being taken captive by the French. When Mountfort himself needed support locally, he now turned to Humphrey Stafford, duke of Buckingham, and in August 1450 the duke even nominated him for election as a Knight of the Garter, albeit without success. Mountfort was returned to his eighth and last Parliament later that year.
Much of the unrest that affected Warwickshire in the 1450s arose from Mountfort’s decision in his old age to disinherit Sir Baldwin (his eldest son by his first marriage) in favour of another son, Robert, and, more particularly, of his youngest child, Edmund (the issue of his second marriage). In the will which he made on 10 Nov. 1451 he demonstrated his clear preference for Edmund as well as his concern for the welfare of the latter’s mother. In order that new entails of his estates should be put into effect he made Buckingham one of his feoffees, thus forcing Sir Baldwin to seek the assistance of Richard Neville, the new earl of Warwick. Outright hostilities did not, however, break out until after Mountfort’s death, which occurred on 6 Dec. 1452, when Buckingham’s influence enabled Edmund and his mother to enter Coleshill and five other manors which should, by rights, have gone to Sir Baldwin. Edmund could also look for support to the duke of Somerset, the earl of Wiltshire and even to the queen herself, with the consequence that Sir Baldwin and his son, Simon, kept imprisoned in Buckingham’s strongest castles between 1456 and 1458, had no alternative but to sign away all their legal rights to the family estates. However, Sir Baldwin eventually sought the assistance of Edward, earl of March (the future Edward IV), and the death of Buckingham and ascendancy of Warwick finally enabled Simon to take possession of the disputed property.