The subject of this biography was quite probably a son or close relative of the Peter Grimsby who represented Hull in three Parliaments during the third quarter of the 14th century. He seems also to have been a kinsman of Sir John Grimsby and his son, Robert, the latter of whom was heir, through his mother, to an extensive estate in and around the Lincolnshire village of Wainfleet. In March 1388, Robert settled his reversionary interest upon a group of trustees, including Simon Grimsby, who maintained an active interest in his property transactions there, and in Hull, for the next ten years at least.
Simon’s attempts to consolidate his position as a landowner involved him in at least four lawsuits, the most notable of which concerned his wife’s claims to property worth 40 marks a year in Newcastle-upon-Tyne, which had allegedly been settled upon her for life by her first husband, Thomas Wodeman. In a petition addressed to the court of Chancery at some point after 1391, the couple complained that three Newcastle men had evicted them ‘through champerty and maintenance’, and had subsequently refused to accept repeated offers of settlement by arbitration. The outcome of the case is not recorded, but Simon had already managed to secure some of his wife’s jointure by 1394, when he was in possession of a third share of five messuages and other holdings in Newcastle. According to the tax returns of 1412, his income from property there and in Hull stood at £20 p.a., which suggests that he eventually recovered most of the land at issue. During this period he was also embroiled in litigation with the mayor and commonalty of Hull over the ownership of a messuage in Hull and a plot of land in Myton, as well as facing allegations of fraud with regard to another local transaction. Early in the 15th century John and Joan Bingley accused him of using ‘son subtile ymaginacion ... son mauies conseil et exitacion, et auxi ... soun donnes et bealx promesses’ to suborn one of their trustees so that he himself could gain control of their property. Whatever the truth of these accusations, no lasting harm was done to Simon’s career, which went from strength to strength. For over 28 years he not only served regularly as a collector and controller of the royal customs in the port of Hull, but played a prominent part in local government too, discharging a term as bailiff and no less than four terms as mayor, besides representing the borough in at least four Parliaments.
Not surprisingly, in view of his wealth and influence, Simon was often involved as a mainpernor, witness or executor in the affairs of other northerners. On at least four occasions between 1382 and 1403 he offered securities for Yorkshiremen with business either in the court of Chancery or at the royal Exchequer; and from time to time he attested deeds for such friends and neighbours as William Terry I. He was, moreover, involved with John Leversegge in arrangements for the endowment of a hospital at Myton by Sir Michael de la Pole (who recovered his father’s earldom in 1398). A good deal of his time seems to have been devoted to responsibilities of this kind, which occasionally proved onerous. He and Leversegge were, for example, embroiled in a protracted lawsuit for the recovery of debts owed to the Hull merchant, John Colthorp (d.1395), who had made them both his executors; and in 1403 he was entrusted by the archbishop of York with the task of administering the estate of Thomas Snainton, a chaplain who had died intestate. Two years before, Grimsby had witnessed the will of William Snainton’s widow, Joan, so it looks as if their two families were related in some way.