The prominence given to the Trevarthian family in the public records in the last decades of the 14th century rests on the proclivity of at least two of its members towards lawless behaviour. The example of our MP’s father, an outlaw for the last ten years of his life, was followed in many respects by his son. Born about 1360 the latter was early involved in some kind of disturbance, and in 1376 he and his father (and a number of others) were outlawed. Sentence was suspended, however, when they were prepared to answer charges, but their arrest soon followed. In June 1379 John senior was a prisoner in the custody of the marshal, having been indicted for no less a crime than treason (although he clearly escaped the penalty). Later that year it was alleged that Philip Tregoz had lain in wait at night in order to kill the Trevarthians, and had ‘broken their houses, assaulted their servants, and taken away their doors, value 20s.’, but it is clear that the accused was acting in retaliation for wrongs done to him by the pair. In May 1380 both Trevarthians were to be brought to the Marshalsea ‘for certain misprisions against the King’, and in July orders were still out for their arrest for offences now said to have been committed in the King’s presence, as well as for ‘homicides and depredations’.
Father and son then became involved in a feud with the Eyr family, in which their principal accomplices were John Penrose (afterwards j.KB), Alan St. Just and John Rensy. At some point in 1381 they entered the manor of ‘Trembetha’ which William, Lord Botreaux, had only recently recovered from them at the assizes, destroyed buildings and stole the possessions of Botreaux’s tenant, Richard Eyr. Not content with this, they then secured the indictment of Botreaux and Eyr on charges of treason and ‘sent people to watch for and kill’ the latter. Such were the intimidatory tactics of the Trevarthians that Lady Botreaux asserted that they were ‘so powerful in the country that none can have common law or right against them’. Then, in 1382, Trevarthian junior and others were accused of breaking the arrest of a ship at anchor in Mount’s Bay and also of attacking a Portuguese vessel which had surrendered to the King’s admiral of the west, which, with its cargoes of wine and other merchandise, they were still detaining in December that year. Orders were out for the Trevarthians’ arrest again in February and May 1383 for ‘certain treasons’ and, more specifically, ‘treasons at sea’; and John junior was indicted before the j.p.s for having, with his father’s counsel and abetment, broken into the priory of St. Michael’s Mount through a window and stolen valuable ornaments and casks of wine. When this last case eventually came before the King’s bench (in 1391) Trevarthian was to explain his earlier failure to appear in court to answer the charges as owing to his absence on royal service in Flanders, in the company of Henry Despenser, bishop of Norwich; and he produced a certificate which showed that, having been retained on 27 Apr. 1383, he had been abroad from 16 May following until 30 Oct.
The outlawry of Trevarthian’s father had complicated the succession to the family estates, but the younger John’s first marriage brought him other properties which may have compensated for the loss. By a settlement agreed in 1379 lands in 19 places were made over to him and his wife by his father-in-law, Ralph Arundell, and three years later his father gave him a rent charge of £20 a year from other holdings. He and his wife were also promised the manor of Carhayes and lands in Portholland and Pengilly after Arundell’s death. Those properties remaining in his father’s hands were, however, declared forfeit to the Crown and, from May 1384, were granted out on leases at the Exchequer for £14 or £20 a year (although their true annual value may have been as much as £35). In addition to this, Trevarthian senior was supposed to enjoy a corrody at St. Michael’s Mount priory, but in view of his son’s depredations, this was most likely withheld by the prior. The younger Trevarthian’s stepmother, Idonea, was granted by the Crown in 1389 the premises in London which had belonged to her former husband, Sir Simon Cuddingtont, and after Trevarthian senior’s death (on 25 Apr. 1395) she was also allowed to take possession of lands in Surrey (presumably also pertaining to the Cuddington estate) worth £5 6s.8d. Meanwhile the forefeited territory elsewhere had been awarded by Richard II in 1392 to Trevarthian junior. The grant referred to him as ‘King’s esquire’ and was made free of rent but on the understanding that he supported his father, a rather curious arrangement, possibly arising from some personal service he had done the King. (It may be speculated that his attacks on the property of the earl of Warwick had given Richard satisfaction.)
Following the death of his father, Trevarthian apparently succeeded to his Cornish patrimony without further difficulty. Two years previously he had married the twice-widowed Joan Trenewith, heiress to the Bodrugan estates, and this had immediately involved him in a dispute over some of the property with her half-brother, William Bodrugan I ‘the bastard’, and her son, William II (born Trenewith). Subsequently, this lady was accused of trespass at Restronguet, a Bodrugan manor, by Sir John Herle and John Colshull I, and was imprisoned at Lostwithiel, only to be freed on bail in 1396 on receipt of information that she was ‘shortly to become a mother’. It was in that same year that Trevarthian shared with (Sir) John Arundell I of Lanherne the estate of Thomas Carminowe and his daughter, comprising four-and-a-half manors, three advowsons, and other premises in Cornwall, which fell to him by maternal inheritance. In 1399 Trevarthian placed all his holdings in the hands of feoffees. These territorial interests must have made him a man of considerable substance in Cornwall, and one who, despite his turbulent youth, was an acceptable candidate for Parliament, especially in view of his new-found favour at the royal court. It is noticeable, however, that Richard II’s esquire and public servant ceased to act after 1397, and, in common with other prominent men of the West Country, returned to participation in local government only after the accession of Henry IV. Trevarthian represented Cornwall in 1401 both in Parliament and in a great council.
In March 1401 Trevarthian arranged the marriage of his son, Otto, to a daughter of one of the oldest of Cornish families. In return for 140 marks and agreements regarding land, backed up by bonds of £100 and £1,000 respectively, Elizabeth, the widow of Sir Warin Archdeacon, agreed that the boy might marry Elizabeth, her late husband’s daughter and coheir. The other three daughters were married to Sir Walter Lucy, Thomas, son of (Sir) John Arundell, and Sir Hugh Courtenay and in the following year Trevarthian, Lucy and Sir John joined together to secure from the prince of Wales a lease of part of the Archdeacon estates. The lawless Trevarthians had become both respectable and substantial. Indeed, at the time of his death, Trevarthian was holding the office of sheriff of Cornwall, by the prince of Wales’s appointment.