Herbert, Thomas (1656–1733), 8th earl of Pembroke, lord lieutenant of Ireland , was born probably at Castle Baynard, near Blackfriars, London, third son of Philip, 5th earl of Pembroke, and his second wife, Katherine (d. 1678), daughter of Sir William Villiers of Brooksby, Leicester. His father and grandfather had been involved on the parliamentary side during the civil war. He was educated at Christ Church, Oxford. Herbert was MP for Wilton 1679–81, being considered a moderate tory although he made no mark in parliament. He succeeded to the earldom in 1683 and served as lord lieutenant of Wiltshire 1683–7, when he was removed over his refusal to cooperate in remodelling the corporations. He was first lord of the admiralty 1690–92, lord privy seal 1692–9, lord president of the privy council from May 1699 to 1708 with a brief break in 1702, and first English plenipotentiary at the negotiations leading to the treaty of Ryswick in 1697.
Pembroke was appointed lord lieutenant of Ireland on 30 April 1707, in place of the tory 2nd duke of Ormond (qv). He was sent to Dublin with specific instructions to form a mixed administration, following the growth of party divisions between whigs and tories during Ormond's term of office. To this end, whigs including Richard Freeman, who replaced Sir Richard Cox (qv) as lord chancellor, and Alan Brodrick (qv), who became attorney general, were brought into government. George Doddington, the radical English whig, came over as chief secretary. Pembroke was entrusted with bringing in a repeal of the sacramental test which had been imposed on protestant dissenters by a clause in the act to prevent the further growth of popery passed in 1704. This proved to be impossible, with the proposals being met with hostility in the Irish parliament. The second major issue that confronted Pembroke during the 1707 parliamentary session was the question of supply. Here his patient, compromising nature paid off. The whigs were put at a disadvantage by their previous uncooperative stance on fiscal matters under the Ormond administration. Exasperated by their prevarications and divisions, Pembroke sought and got tory support for a compromise proposal which saw supply granted for a year and three-quarters. Whig attacks on the Ormond administration's management of the revenue, and on the tory-dominated privy council, were considerably blunted when the revenue was revealed to be in a generally healthy state.
Pembroke spent about a third of his eighteen-month tenure in Ireland. His term coincided with the 1708 Jacobite invasion threat, which revealed the poor state of Ireland's military preparedness and led to the revoking of catholic arms licences, the detention of large numbers of priests and known Jacobites, and an effort to revive the moribund militia. The shortness of his tenure, and the absence of sweeping changes in the administration or the judiciary, means Pembroke must be seen as a transition figure in Irish politics, bridging the gap between tory domination in the Rochester and Ormond administrations and the short-lived whig takeover which followed Thomas Wharton's (qv) appointment in late 1708. His lack of success in building up a mixed court party, demonstrated by the increasingly bitter exchanges between Irish whigs and tories, means that his viceroyalty must be seen as a failure.
Pembroke did, however, manage to secure an increased pension of £3,000 before his departure from office, and promptly retired from active government service. He continued to attend the English house of lords, where his voting behaviour marked him out as a Hanoverian tory. Pembroke was by all accounts a learned and refined man, who was president of the Royal Society 1689–90. A patron of the arts, he built up an extensive art collection at his house at Wilton, Wiltshire. After a long retirement, he died 22 January 1733 at his house in St James's Square, London, and was buried in Salisbury cathedral.
He was married three times and had numerous children. He married first (1684) Margaret (d. 1706), daughter and heir of Sir Robert Sawyer, then English attorney general. He married secondly (1708) Barbara (d. 1722), daughter of Sir Thomas Slingsby and widow of Baron Arundell of Trerice and previously of Sir Richard Mauleverer. In 1725 he married Mary, daughter of Viscount Howe, who survived him. His son Henry (by his first wife) succeeded to the earldom. Another son, Robert Sawyer-Herbert, was appointed to the Irish revenue commission in 1728, despite his only qualifications being his parentage and previous position as a gentleman of the bedchamber to King George I.