[1] The family were Parliamentarians, and early in 1643 Thomson held the commission of captain of a troop of horse under William Russell, 5th Earl of Bedford.
In the following year he served under Sir William Waller in his western campaign, and at this period attained the rank of colonel.
[2] Thomson was returned to parliament for Southwark, probably in August 1645, and on 18 February 1651 was appointed a member of the English Council of State.
After the Restoration of 1660, Thomson went to ground at the residence of his brother Maurice at Lee, Kent, and occupied himself with anti-Royalist intrigues.
After some time in obscurity, Thomson around the beginning of 1668 was nominated to the commission of accounts, and returned to public life.