James followed in his father’s profession as a lawyer, and was returned to Parliament for the first time while his father was joint justiciar of South Wales. Shortly before that, in October 1389, he and Richard were together associated with the latter’s friend Thomas Oldcastle (who was to represent the shire in the same Parliament) and Thomas Walwyn II, receiver-general to Roger Mortimer, earl of March, as co-feoffees of property in Lower Bullingham near Hereford. In November 1390 James was re-elected for the city, while his father sat for the shire. The following year, along with another of Richard’s associates, the lawyer Philip Holgot, James was entrusted by Sir John Eynesford to complete an entail of part of his estates. In September 1393 he was nominated as the attorney in England of John Acton, then second chamberlain of the Exchequer in Ireland, and in May 1397 he undertook similar duties for Sir John Cheyne of Herefordshire.
On 12 May 1400 the Exchequer was instructed to pay Nash £5 as the first half of his annual fee, and four days later, in his official capacity, he received the attorneys of the prior of Llanthony Prima. He died, however, before 9 June, this being the date of the commission set up to inquire what lands he, described as a bastard who had died leaving no heirs, had held in the city and shire of Hereford.