Although there were Derhams living in Bishop’s Lynn from before 1347, Thomas was a native of East Dereham, several miles away. He was described as ‘alias Thomas Moule of East Dereham’ in March 1388, when the letters patent of protection granted him as sailing to Brest in the retinue of Sir John Roches were revoked because he had failed to join the expedition. His father, who held part of the manor of ‘Wesenham’s’ was also, in 1398, possessed of a part of a knight’s fee in Crimplesham near West Dereham, and it was there that Thomas was to take up residence.
Derham soon gained a reputation as a competent lawyer, building up a busy practice in the service of many important clients, whose interests he safeguarded as an attorney in the lawcourts and as a trustee of their estates. His career effectively began in the late 1390s when he acted on behalf of Sir Leonard Kerdeston of Norfolk and the master of the local hospital of Beck, among others. Subsequently, he made numerous appearances as a surety in Chancery and the Exchequer. Although most of his business came from the gentry of Norfolk, in 1403 he was one of a syndicate who purchased from the Braybrookes Lord Grey’s manor of Hartley in Kent, only to sell it subsequently to John Urban, the Cornishman. In the same year he provided securities at the Exchequer for Elizabeth, widow of Robert, 5th Lord Scales, whose cousin, Sir Simon Felbrigg KG, became a close associate of his in many transactions and, indeed, was to act in later years on his own behalf as a feoffee. In 1405 and 1406 he went surety for lessees of certain estates forfeited by Thomas Mowbray, the late Earl Marshal: namely, Sir Thomas Erpingham KG and Mowbray’s retainer, William Rees. In Erpingham he found an influential contact at Henry IV’s court, a link which the burgesses of Bishop’s Lynn may well have borne in mind when electing him as their parliamentary representative at that time. For Rees he was later to appear as a trustee of manors in Norfolk and Cambridgeshire.
Derham’s election by Bishop’s Lynn to the Parliament of 1406 perhaps owed something to his activities in the town as a royal commissioner five years previously when, while investigating complaints made against Bishop Despenser of Norwich, he had enjoyed the burgesses’ hospitality. But more recently, in 1404-5, the town had paid him £1 for his legal advice. In later years, at least from 1413 to 1418, he was to be retained for his counsel to the local authorities at a fee of £2 a year.
Very likely the most powerful of Derham’s patrons were Bishop Beaufort of Winchester (for whom he witnessed letters patent at Southwark in 1409), and the bishop’s brother Thomas, who in 1416 became duke of Exeter. Derham was co-feoffee with the latter in property at Lynn and after the duke’s death (in 1426) he continued to look after his posthumous concerns not only as a trustee but also as an administrator of his estates in Suffolk and Hampshire.
In the course of his career as a lawyer Derham provided services for several other members of the gentry of East Anglia. In 1411 he had become a trustee of the estates of the recently-deceased Constantine, Lord Clifton; a year later he was acting in a similar capacity in the manors held by Sir Thomas Gerberge’s wife; in 1415 he was a feoffee of Walsham, Suffolk, on behalf of Sir William Elmham’s widow, and before long he was engaged by Sir Roger Swillington for legal transactions regarding his lands in Suffolk and Yorkshire.
It is not surprising that Derham, being of good reputation as a lawyer and well regarded as a member of the Norfolk and Suffolk benches, was often chosen to arbitrate between the parties to difficult lawsuits. In 1425, in the duke of Gloucester’s presence at London, he was named by William Paston (the future j.c.p.) as one of the referees in his quarrel with Walter Aslak. And it may have been in connexion with the settlement eventually reached that, along with Paston, he was party to transactions with John Aslak of Crostwight a few years later. About this time, one John Bexwell, professing himself in a petition to Chancery to be ‘gretely hurt’ by Derham’s evasion of payment of rents (on the false grounds that he was an alien), asked that their ‘umper’, Sir Thomas Tuddenham†, should hand over the lawyer’s £100 bond. In May 1434 Derham was among the Norfolk gentry required to take the general oath not to maintain breakers of the peace.
Derham died between 12 Aug. 1444, when he made his will, and 23 Mar. 1445, when it was proved in the prerogative court of Canterbury. His testamentary depositions were straightforward enough: he requested burial in the parish church at Crimplesham, to which he left, for repairs, ten quarters of malt, and, for masses for his soul, three years’ profits (£40) from his property near by. Here he had evidently maintained a richly-furnished house and well-stocked lands. Elizabeth Derham (presumably his wife) and her daughter, Alice, were bequeathed various beds (including those with woven hangings depicting scenes from the lives of St. George and St. Michael), bedding, linen, curtains, carpets, silver vessels, a prayer book and also livestock, while her son, Thomas, was to receive, as well as similar items, a horse called ‘Scote’, six cows, 20 ewes, carts, carriages, farming equipment, a fishery and specified provisions. Sir Thomas Tuddenham was named as a supervisor of the will.