His uncle, Henry Fanshawe, took him under his protection, and procured for him the reversion of the appointment of the office of Remembrancer of the Exchequer, then occupied by the elder Henry. This office was held during five tenures by members of the family. Fanshawe acquired considerable wealth in his office, to which he succeeded on his uncle's death in 1568. Besides Fanshawe Gate, which he let to his brother, he owned Ware Park, Hertfordshire and Jenkins, in Barking, Essex, and other property. He fulfilled the duties of his office with diligence, as we find by various entries in the State Papers of Elizabeth's reign. In 1597 he wrote to Lord Burghley that 'by my continually attending the business of my office all the term, I have too much neglected my health and business in the country, and as my presence is urgently required there I have left all things in such a state that the duties may be as well performed without me. I hope I may repair thither and stay until the term.... If there shall be any occasion for my attendance, I will speedily return, though to my hindrance both in health and profit.' Fanshawe sat in the parliament of 1571 for Rye, in five succeeding parliaments for Arundel, and in 1597 for Much Wenlock, Shropshire. In 1579 he established, in accordance with the will of his uncle, the free grammar school of Dronfield.
and had issue by both marriages. His elder son by his first marriage, Henry, succeeded him as remembrancer. Thomas, his eldest son by his second marriage, inherited Jenkins and other estates at Barking and was an MP for Lancaster. William, his youngest son, was also an MP. Alice, his eldest daughter by the second marriage, married Sir Christopher Hatton, a relative of the Lord Chancellor and favorite of Queen Elizabeth, Sir Christopher Hatton. Thomas Fanshawe's widow was buried at Ware on 30 May 1622.
Works
The Practice of the Exchequor Court, with its severall Offices and Officers. Being a short narration of the power and duty of each single person in his severall place. Written at the request of the Lord Buckhurst, sometime Lord Treasurer of England, 1658. This work has since been attributed to Fanshawe's colleague Peter Osborne.
An Answer to Articles concerning the Lord Treasurer's Office.