Coming from the Westmorland family which held the manors of Preston Patrick and Preston Richard, John, the future judge, was probably a younger son, for he apparently inherited Preston Patrick only after the death of his brother, Richard. His father, another John, represented their native shire in Parliament six times between 1362 and 1382 and served on many royal commissions in that county as well as in Yorkshire and Cumberland before his death, which occurred some time between 1392 and July 1395. At the latter date John, junior, as his son and heir and tenant of his lands, appeared in Chancery to take oath that a certain commission had never been delivered to his late father. Before 1395 it is sometimes difficult to disentangle the careers of father and son, especially as the younger man had been active for some 15 years previously. Preston junior retained interests in Westmorland throughout his life, and in later years he was appointed to judicial commissions in the north of England,
Quite early on, Preston’s ability as a lawyer brought him to the attention of John of Gaunt, who appointed him in 1393 as steward of his estates in Sussex, a post in which he was to be retained by Henry of Bolingbroke until 1404. But his services were by no means offered exclusively to the house of Lancaster; on occasion the Crown employed him as an attorney, as, for example, in 1394 when he was rewarded with £2 6s.8d. for his labour in the successful prosecution of a man charged with ten murders. In 1395 he was authorized to take an oath from Henry Michelgrove’s widow before she was assigned dower, receiving a year later custody at the Exchequer of the rest of Michelgrove’s property in Kent and Sussex during the minority of the heir. Also in 1396 he shared keeping of the estates of Richard, Lord Talbot. Following the death of Archbishop Courtenay of Canterbury, Preston was among those made guardians of the temporalities of the see, although the grant was to be cancelled before it had taken effect. He was probably already holding office as steward of the archbishop’s manors of South Malling and Otford, which he was to retain after Archbishop Arundel was exiled by the Parliament of September 1397. For more than a year previously he had been acting as ‘bailiff’ of certain of the estates of the archbishop’s brother, Richard, earl of Arundel. Clearly, however, he was not so strongly identified with the Fitzalans as to forfeit his place on royal commissions; on the contrary, it had only been after Earl Richard’s arrest (which was to lead to his condemnation for treason) that he had joined the ranks of j.p.s in Sussex and Surrey. Preston could exert sufficient influence in Chancery to secure in November 1398 a special commission headed by the earls of Northumberland and Westmorland to bring to trial before the King’s Council his adversary, John Middleton, who with his followers had allegedly sought to ambush and kill him and his friends in the north of England. It was no doubt Preston’s position as duchy of Lancaster steward which prompted his election for Sussex to the Parliament of 1399 in the company of the prominent Lancastrian, John Pelham, friend of Henry of Bolingbroke, whom they were to acclaim as King. While Parliament was in session that November he secured a share in the farm of the estates of the alien priory of Wilmington for the duration of the war with France. However, a few years later, in February 1404, Pelham placed Preston under arrest at Pevensey castle, from whence he was escorted before the King’s Council to answer certain charges. Doubtless his detention arose from his performance as steward of the estates of the duchy of Lancaster in Sussex, a post in which Pelham was to succeed him just a few months later.
However, after 1404 Preston’s rise in the legal profession had largely taken him away from Sussex to London, where he held the civic office of recorder for at least nine years. During this period of his career he acted as a mortgagor of the Essex estates of Richard de Vere, earl of Oxford, and as a trustee of a manor in Yorkshire pertaining to the inheritance of John Mowbray, the future duke of Norfolk.
Preston died on Michaelmas day 1434. Eleven years later his house, ‘Le Grete Belle’ near the Barbican, along with the 14 dwellings annexed to it, was forfeited to the Crown on the ground that it had been put into the hands of trustees (who included two members of his family—his younger son, Robert, and Nicholas Preston, clerk) to the use of the chaplains serving a chantry which he was said to have founded in St. Gregory’s chapel near Preston Richard, thus being in breach of the Statute of Mortmain. However, a subsequent search in the records of Chancery found no evidence that the chantry had ever been founded, and further inquiries established that the trustees had held the property only to the use of Preston and his heirs.