Thomas was probably related to John Carathyn, who provided securities for the burgesses elected to Parliament for Helston in 1397 and 1406. The full extent of his landed possessions is not known, but part of his income, annual rents of £1 6s.8d, came from property in Helston and from land nearby at Bonallack and ‘Mewechyn’. He also held land at Lanestley in Gulval, not far from Helston, and he may have been the Thomas Carathyn whose possessions in 1451 were then valued for the purposes of taxation at 40s. a year.
Over the years, beginning in 1406, Carathyn made appearances in Chancery as a surety for fellow Cornishmen, among them John Penrose of Methleigh; and on his own account he brought an action in the central courts against John Mychel of ‘Menythe’, for a debt of £5. He attended the shire elections held at Lostwithiel in November 1420, and was returned to Parliament himself a few months later. In 1425 he was associated with Nicholas Radford and Otto Tregonan, two prominent West Country lawyers who had also been Members of the Parliament of May 1421, as a trustee of the estates in Cornwall, Devon and Oxfordshire belonging to John Basset, esquire.
