As the son of one prominent Nottinghamshire MP and the brother of another, William Leek was sure of an influential position in county society. He had come of age by March 1378, when he joined with his father in offering a bond worth £160 to a local landowner, although no more is heard of him for the next seven years, during which period he married the daughter and heir of Sir John Stockton of Screveton, thus acquiring a substantial estate of his own. It was in about 1385 that he settled her inheritance in Screveton, Car Colston and Kirby Bellars upon feoffees (including his brother, Sir John); and not long afterwards other property in Alverton came into their hands as well. Following Sir John’s example, William decided to contract for a term of military service overseas; and in September 1388 royal letters of protection were accorded to him as a soldier under Sir William Beauchamp’s command in Calais. In the event, however, he refused to leave England and the privilege was promptly withdrawn.
Henry Henry IV’s seizure of the throne in the following September brought with it a dramatic improvement in the fortunes of William Leek and his kinsmen; and together with his young nephew, John, he was retained as an esquire of the royal body at a fee of ten marks p.a. It is thus hardly surprising that the electors of Nottinghamshire, who were generally well disposed towards the Lancastrian cause, should return him to the first Parliament of the new reign, although his brother, as sheriff and returning officer, was clearly in a position to exercise a good deal of influence on his behalf. The two men were, indeed, summoned together to attend a great council which met in August 1401 at Westminster. William had, moreover, by then assumed the first of his three offices on the duchy of Lancaster estates in the north Midlands, as well as beginning to serve fairly regularly as a royal commissioner. Although he does not appear to have sat again in the House of Commons, he did attend the Nottinghamshire parliamentary elections of 1411, 1413 (May), 1414 (Nov.) and 1417, accompanied on the first occasion by his eldest son, William.
Leek’s personal activities are less well documented, for most of the evidence which now survives about him concerns his appearances as a feoffee-to-uses and witness to deeds for his friends and family. We do, however, know that at some point before July 1407 he began an unsuccessful lawsuit against an Essex couple; and that at various times he was caught up in litigation nearer home at the Nottingham assizes—no doubt in his capacity as a trustee.