[1] He was born at the family home of Broughton Castle near Banbury, in Oxfordshire, the only son of Richard Fiennes, 7th Baron Saye and Sele, and his wife Constance, daughter of Sir William Kingsmill.

In 1622 he opposed the benevolence levied by the king, saying that he knew no law besides parliament to persuade men to give away their own goods; he spent six months in the Fleet Prison, and then had a period of house arrest.

[2] During the personal rule of Charles I, Saye devoted time and money to schemes of colonisation: his motives were in part financial, but also religious and political.

[2] In 1630 he established, together with Robert Greville, 2nd Baron Brooke, John Pym, and others from the group of Puritan entrepreneurs, a company to settle the Providence Island colony.

[2] Saye obtained a patent for a large tract of land on the Connecticut River on 19 March 1632 from Robert Rich, 2nd Earl of Warwick and the New England Company, again in association with Lord Brooke and ten others.

[2] Saye concentrated his energies on the settlement of Providence Island, while spreading disparaging reports about New England, including its climate and land.

Leading puritans, including John Pym, who were members of the Providence Island Company met Saye at Broughton Castle to coordinate their opposition to the King.

Although Saye resisted the levy of ship money, he accompanied Charles on his march against the Scots in 1639; but, with only one other peer, he refused to take the oath binding him to fight for the king "to the utmost of my power and hazard of my life".

He was a member of the committee of both kingdoms; was mainly responsible for passing the self-denying ordinance through the House of Lords; and in 1647 stood up for the army in its struggle with the parliament.

He agreed to donate £100 to the town of Wisbech in the Isle of Ely, with the interest to be used for providing clothing for the poor and administered by his son Richard Fiennes.