Jervoise’s inheritance comprised substantial estates in Wiltshire, Worcestershire and Shropshire.
Jervoise became the first of his family to enter Parliament, being returned for Whitchurch at the general election of 1620; he was subsequently re-elected to every Parliament until the outbreak of the Civil War. He left no mark on the records of the 1621 assembly, but his papers attest to his interest in its proceedings, as they include a list of all his fellow Members of the Commons, and copies of various petitions and bills, including the bill to prevent the law courts from charging excessive fees. Jervoise had long experience of litigation, having struggled since early childhood against his stepfather in the Court of Wards. Consequently he may well have attended the committee appointed to consider this measure, which was thrown open to anyone who wished to participate in its deliberations (3 May 1621).
In 1624 Jervoise spent £5 14s. 3d. in entertaining the voters at the Whitchurch election. He also compiled a list of those who supported his wife’s uncle, Sir Henry Wallop*, for the first seat.
Jervoise reclaimed the first seat at Whitchurch in 1625.
In the 1626 Parliament Jervoise evidently brought his 1624 diary with him to Westminster, as he used it to jot down some of the articles pertaining to Buckingham’s impeachment; a series of correspondence between Viscount Conway (Sir Edward Conway I*) and the earl of Bristol, the former ambassador to Spain; and Charles’s speeches in Buckingham’s defence.
Jervoise served as a conscientious collector of the Forced Loan, although he did his best to gain exemption for himself.
In 1634 the death of Henry Sherfield*, for whom Jevoise was trustee and surety, caused him serious financial embarrassment, and he applied for protection from Sherfield’s creditors, which was periodically renewed thereafter.
