Nathaniel Fiennes, 1610-69
Disgraced for surrendering Bristol to the Royalists in 1643, he became a moderating influence in Parliament and a supporter of Cromwell's Protectorate
The second son of William Fiennes, Lord Saye-and-Sele, Nathaniel Fiennes was educated at Winchester College and New College, Oxford. Like Lord Saye, he was a devout Puritan and travelled to the Calvinist city of Geneva after his graduation. In 1636, he married Elizabeth, the daughter of the Parliamentarian Sir John Eliot who had died a prisoner in the Tower of London in 1632.
Fiennes sat as MP for Banbury in the Long Parliament where he became a prominent opposition leader, closely associated with John Pym. He played a leading role in exposing the "Army Plot" of 1641 and was an outspoken critic of Episcopacy. On the outbreak of civil war in 1642, Fiennes, his father and brother John Fiennes attempted unsuccessfully to prevent Spencer Compton, the Royalist Earl of Northampton, from seizing Lord Brooke's cannon at Banbury, but he joined Brooke and John Hampden in the force that relieved Northampton's subsequent siege of Warwick Castle.
Commissioned a colonel in the Earl of Essex's army, Fiennes fought at Powick Bridge and Edgehill. The following year, Essex appointed him governor of Bristol. Fiennes complained that he didn't have enough men or supplies for Bristol's defence; he was obliged to surrender the city when Prince Rupert stormed it in July 1643. Accused by his political enemies of cowardice and treachery, Fiennes was tried by court martial and sentenced to death. The Earl of Essex intervened to revoke the sentence, but Fiennes' reputation was ruined. He left England for two years in disgrace.

When Prince Rupert surrendered Bristol to Fairfax in 1645, in similar circumstances to Fiennes' surrender in 1643, the Commons voted to restore him to his seat in Parliament. He became a stalwart of the "Middle Group" associated with Oliver St John that tried to find a middle way between the Independents and the Presbyterians. Fiennes supported the Army Grandees in trying to negotiate a settlement with the King and lost patience when Charles escaped to the Isle of Wight in November 1647. However, Fiennes opposed the radical position adopted by Army leaders after the Second Civil War and supported the King's final answer to the Treaty of Newport in 1648, for which he was excluded from the House of Commons in Pride's Purge.
Fiennes remained aloof from public life during the Commonwealth (1649-53) but supported the establishment of Cromwell's Protectorate. He was elected MP for Oxford in the First and Second Protectorate Parliaments. In 1654, he was appointed to the Council of State and was a Commissioner of the Great Seal in 1655. Fiennes was a leading member of the faction that offered the Crown to Oliver Cromwell. After Cromwell's refusal, Fiennes accepted a seat in the new Upper House, even though his father Lord Saye-and-Sele refused to recognise it. Fiennes supported Richard Cromwell as Oliver's successor and was driven from office with the collapse of the Protectorate in 1659, after which he retired into private life.
Sources:
M.L. Schwarz, Nathaniel Fiennes, Oxford DNB, 2004
David Underdown, Pride's Purge (Oxford 1971)