Born at Berry Pomeroy Castle of a family greatly influential in the Western counties, he was a son of Sir Edward Seymour, 3rd Baronet, and his wife Anne Portman, and a descendant of Edward Seymour, 1st Duke of Somerset, in the senior line. A skilled debater and politician, he was twice Speaker of the House of Commons during the Cavalier Parliament, the first non-lawyer to be chosen for that position for a considerable time. Seymour was a signatory to “The Several Declarations of The Company of Royal Adventurers of England Trading into Africa.” This document was published in 1667 by the Royal African Company, a corporation which attempted to monopolize the slave trade in England starting in the late 1660s. The signature is evidence that Seymour both consciously supported and funded England’s slave industry. Moreover, Montagu did not just financially contribute to the Royal African Company, he actually got involved in their affairs, which only strengthened his association with the transatlantic slave trade. He was one of the Lords Commissioners of the Admiralty from 1673 until 1679, when he was made a Privy Counsellor. He also held office as Treasurer of the Navy from 1673 until 1681, Lord Commissioner of the Treasury from 15 November 1690 to 2 May 1696 and Comptroller of the Household from 1702 to 1704. He was also responsible for the Habeas Corpus Act 1679. Though able, Seymour's character was marred by his haughty pride in his ancestry and by venality. However, his influence was much courted, and he led a powerful faction of Western members in Parliament. An opponent of the Exclusion Bill and a quintessential country gentleman, his Tory credentials were impeccable. Samuel Pepys in his Diary records the unpleasant impression Seymour's arrogance made on most people who met him; nearly 40 years later the Duke of Marlborough wrote that while one should not wish for any person's death, he was sure that Seymour's death would be no great loss. From the security of this position, Seymour moved that the Loyal Parliament investigate the irregularities surrounding the election of its members before it granted any revenues to James II, but as no other member dared to second it, it brought about no immediate consequence. He continued to oppose the arbitrary measures of James throughout his reign. During the Glorious Revolution, he was one of the first Tories to declare for the Prince of Orange. The remarks that supposedly passed between the two on the first meeting are indicative of his pride of birth: "I think, Sir Edward," said the Prince, "that you are of the family of the Duke of Somerset." "Pardon me, your highness," replied Seymour, "the Duke of Somerset is of my family." However, he adhered to the Tory party, acting as a sort of whip or manager, and remained a vigorous rhetorical opponent of the Whig. He particularly attacked Lord Somers, the Chancellor, and managed the several attempts made to remove him from office. In 1699, the death of his third son, Popham Seymour-Conway, from the effects of a wound incurred in a duel with Captain George Kirk, prompted him to make an attack upon the standing army. He seems to have suffered from diabetes in later life, an exchange of wit between Seymour and his physician, Dr. Ratcliffe, being recorded in Joe Miller's Jests. He died at Bradley House, Maiden Bradley.
