The Tremaynes made their mark on the parliamentary representation of Cornwall and its boroughs in the years between 1344 and 1377; on no fewer than 30 occasions the returns record the election of a John Tremayne. There were perhaps as many as four different individuals involved: the John who sat for the shire 11 times between 1344 and 1369; the John ‘son of John’ who represented Launceston in 1344 and 1352 (and who may have also sat for Bodmin three times and Helston and Liskeard once each in the 1350s); the John ‘junior’ who appeared for Helston and Truro in 1365, for Liskeard in 1368 and for Helston again in January 1377 (and perhaps also for Lostwithiel in 1368 and 1369 and Launceston in 1371 and 1373) ; and the John ‘son of Richard’ who represented Helston in 1369. It is strange that after this impressive display of parliamentary activity the Tremaynes apparently lost interest in the House of Commons; the MP of 1388 was the only member of the family to be elected in our period.
The John Tremayne who had served as a knight of the shire earlier in the century was a lawyer of some distinction, closely involved in the administration of the duchy of Cornwall on behalf of the Black Prince, and retained by William, Lord Botreaux, as a trustee and attorney. It is uncertain when his career ended, but he seems to have been active up to 1376. His marriage brought him the estates in Devon and Cornwall held for life by John Dabernoun of Bradford, but he also built up substantial holdings for himself in the valley of the Helford.
From early in his career Tremayne took an interest in the government of his home county. In 1374 he personally obtained from Chancery the royal commission appointing searchers at Penryn and in the other ports of Cornwall, having affirmed that those named were ‘sufficient for King and people’, and before too long he was given a place on the Cornish bench. A break in his employment as a j.p., which otherwise extended over 25 years, was evidently occasioned by suspect behaviour. It was alleged that he (described as resident at ‘Bodwythgy’ in St. Erth) had taken part in treasonous activities at the time of the Peasants’ Revolt; that ‘by [his] counsel and procurement’ Richard Eyr and his fellows had terrorized Cornwall, beating, maiming and robbing many people; and that, knowing of the insurrection in Essex and Kent, he had gathered together a force of armed men to go to the aid of the rebels. However, as a petition presented in the next Parliament by Elizabeth, Lady Botreaux, makes clear, the indictments (which named her husband as the leader of 80 traitors), had been maliciously and falsely concocted by their enemies, headed by the lawless Trevarthians and John Penrose (the future j.KB), in an attempt to sieze control over certain territory. Parliament agreed to suspend the charges until Lord Botreaux returned from overseas, and in due course Tremayne’s name was cleared. In the following spring he returned to the bench and was one of those commissioned to put down further outbreaks of violence in the south-west. This was not the end of the vendetta, which led to Eyr’s murder and eventually to the downfall of the scurrilous Penrose, although Tremayne, who had known Eyr for many years and secured appointment with the justices of oyer and terminer sent to investigate his death in Surrey in 1383, ceased to be one of the principal contenders.
By this date Tremayne had established a sucessful legal practice, which attracted as clients various Cornishmen including members of the Bodrugan family and (when their earlier enmity was finally set aside) John Trevarthian, for whom he took on trusteeships and appeared as a mainpernor in Chancery and the Exchequer. He was beginning to enjoy a sound reputation in the courts at Westminster, and this brought him briefs from outside Cornwall as well. From 1382 onwards he acted for men from Hampshire, and was employed on royal commissions in that county. He was at Winchester in 1386 when he enfeoffed John Reskymer of all his property in the Cornish parish of St. Erth, and in April 1387 he shared at the Exchequer keeping of the manor of Gatcombe on the Isle of Wight during the minority of the heir, for which he contracted to pay a yearly farm of 20 marks. His appearance as a representative for Truro in the Merciless Parliament was followed within eight months by selection as common serjeant of London, and his preoccupation with matters in the capital no doubt accounts for his temporary removal from the Cornish bench in 1389. He was later promoted to the recordership of the City. Tremayne’s continued employment as a j.p. in the last years of Richard II’s reign suggests that he did nothing to alert the King’s suspicions about his possible adherence to the Lords Appellant of 1388. Yet there may well have been personal links between them, for he was placed on a commission to arrest malefactors who had threatened the earl of Warwick’s tenants in Cornwall, and in 1397 he witnessed transactions in London whereby the earl of Arundel’s niece, Philippa, widow of Sir Richard Cergeaux, formally relinquished her claim to the Fitzalan estates.