Early in his career known as Thomas Holt of Mapperley, Derbyshire, this MP later changed his surname to Mapperley, and it was after him that the Nottingham suburb was subsequently named. On 20 Apr. 1380 he was pardoned for all trespasses of vert and venison committed in the royal park of Bestwood and the forest of Sherwood, and six days later a servant of his was released from Nottingham castle on bail regarding the same offence.
Such schemes were evidently funded by Mapperley’s successful practice as a lawyer, in which he took fees from many clients for whom he acted in both the central and the local courts, before the King’s bench sitting at Nottingham in 1392 and 1396, and at the assizes. In 1376 he had appeared for the prior of Lenton and in 1395 he pleaded for members of the Claydon family of Middle Claydon, Buckinghamshire, when they were defendants in a case brought by Roger Mortimer, earl of March. He was often briefed in ecclesiastical suits: for instance, in 1388 he provided securities for a suspect lollard, and on another occasion he was involved in an appeal in an action against the archbishop of York. That he himself had heretical leanings is hardly in question. Certainly, in April 1399 he and his wife obtained a papal licence for a portable altar.
Mapperley was associated with several of the local gentry. In December 1396 he went surety at the Exchequer for Elizabeth, widow of Henry, Lord Grey of Wilton, and in the following year he was party with her and Sir John Dabrichecourt to a bond of 1,000 marks made with Philip, Lord Darcy, whose son had married her daughter.
