Treffridowe’s father spent some time in royal service in Cornwall, first as alnager, in 1399, and later as a coroner, from 1411. Although he lived at Treffridowe, he was sometimes described as ‘of Yapstowe’, and his landed holdings were the subject of several lawsuits at the assizes at Launceston.
Treffridowe, who appeared briefly as an attorney at the assizes held in 1407, may well have been a lawyer by profession. Whether or not this was the case, he became involved in the administration of the duchy of Cornwall before Michaelmas 1410, when he acted on behalf of the abbot of Newenham in rendering account at the duchy exchequer for the bailiwick of the hundred of Stratton; and later on, at the shire elections to the Parliament of 1422, he stood surety for John Arundell II, eldest son of the steward of the duchy. He probably owed his appointment as joint havener of the western ports of Cornwall to Thomas Chaucer, the chief butler of England, who at that time held the havenership of all the duchy ports on an Exchequer lease. Treffridowe attended the shire elections for Cornwall held at Launceston in 1432 and at Lostwithiel in 1436. By the latter date some discrepancies in his accounts as havenet had been discovered, and after an inquiry conducted at Lostwithiel in 1437 his property was distrained. He died shortly afterwards, and it was as his executrix that in 1441 his widow, Margaret, accounted at the Exchequer for certain sums of money owing from the time of his havenership over 16 years before.