The Ashburnhams first emerged as small landowners in the parish of Ashburnham in east Sussex towards the close of the 12th century. Following the execution for treason of Bartholomew Ashburnham in 1322, the manor passed to his brother John (d.1335) and then to the latter’s son John, the father of the future shire knight.
Of rather different character was the shire knight’s uncle Roger, who became a prominent figure among those engaged in the administration of Sussex in Richard II’s reign, and was able to acquire on his own account at least five manors in that county and in Kent. Young John became head of the family only after his uncle’s death in about 1392, although he is probably recorded earlier. Thirty years previously his father had put in a claim to property in London belonging to a recently deceased kinsman, Henry Grofherst, rector of Horsmonden, so our John Ashburnham may well have been he who as ‘of London’ stood surety in July 1386 for the appearance before the King’s Council of a chaplain named John Ellis in connexion with a suit brought by the archdeacon of Sudbury, and who, in company with the same chaplain, was himself to be arrested and taken before the Council two months later. By 1391 Ashburnham could exert sufficient influence at Court to secure a royal pardon for a Kentish man convicted of manslaughter.
As ‘of Sussex’, in 1400 Ashburnham provided securities in Chancery for a man from Norfolk, which may suggest that he was the Ashburnham who held property at Egmere in that county, in part as a tenant of the earl of Arundel. Two further terms as sheriff were to follow in Henry IV’s reign, but he was never again, apparently, elected to Parliament. Little is known of his personal transactions during this period, although he was evidently on good terms with members of the Halle family, to whom his estates had once been mortgaged, and in particular with John Halle II, on whose behalf he acted in 1404 as a trustee of the Sussex manor of West Preston. In August 1414 he took out royal letters of protection to cover his membership of the retinue of the duke of Clarence at Guines castle, and since these letters were renewed a year later it may be inferred that he also served under Clarence in Henry V’s army at the siege of Harfleur. Shortly before February 1416 he was imprisoned by order of Thomas, earl of Dorset, the admiral, in connexion with his having acted as a pledge for Richard Cryse, party to a prolonged suit in the admiral’s court, notwithstanding that an appeal was pending. A royal commission was set up to hear his case.
By this late stage in his career Ashburnham appears to have been quite comfortably placed, with an annual income from his property at Ashburnham and at Codsheath in Kent estimated at £25. Furthermore, he had expectations of inheriting four of his uncle Roger’s manors on the death of the latter’s widow, and in November 1417 he enfeoffed the two Halle brothers and other friends of his reversionary interest in the same.