Younger brother of Robert Rich, 2nd Earl of Warwick, a Puritan activist and commander of the Parliamentarian navy during the Wars of the Three Kingdoms, Henry was better known as an "extravagant, decorative, quarrelsome and highly successful courtier".

He defected in July 1643 after failing to persuade his cousin and commander-in-chief of the Parliamentarian army, Robert Devereux, 3rd Earl of Essex, to negotiate peace terms.

The next year he was made a member of the Privy Council of England, and sent to Paris to help negotiate the marriage contract between Charles and Henrietta Maria of France, a process completed by James Hay.

[12] This request was granted, along with an appointment as Governor of Landguard Fort, and he benefited from his relationship with Henrietta Maria, who had replaced Buckingham as Charles' closest advisor.

[13] Although he failed to become First Lord of the Admiralty, the 1630s was the highpoint of his career as a courtier; as a Privy councillor, he was frequently consulted on foreign affairs, although his anti-Spanish policy was at odds with that pursued by Charles.

[14] Despite his close links to the court and reputation for extravagance and ambition, Lord Conway described Rich and his brother Warwick as the "temporal and spiritual heads of the Puritans".

While the majority supported Parliament during the civil war, men like Sir William Savile were equally opposed to Catholicism but became Royalists out of a sense of personal loyalty.

While his attendance at company meetings was irregular, he helped secure funding and support for its activities, including Privateer attacks on Spanish merchant ships.

In early 1643, Rich tried to persuade his cousin and Army commander Robert Devereux, 3rd Earl of Essex to force Parliament to make peace; when this failed, he defected to the Royalists at Oxford.

Although present at Newbury in September, he was treated with indifference by Charles and returned to Westminster in November, reportedly because he opposed the "Cessation" negotiated by Royalists in Ireland with the Catholic Confederacy.

[21] By the time Charles surrendered in June 1646, his opponents were divided between moderates led by Holles who dominated Parliament and radicals within the New Model Army, headed by Oliver Cromwell.

[22] On 4 July, a petition was presented to Parliament demanding the resumption of negotiations with Charles, and on the same day, Rich and George Villiers, 2nd Duke of Buckingham raised 400 cavalry in an attempt to seize London.

Rich and 200 men reached St Neots on Sunday 9 July, along with Colonel John Dalbier, an experienced German mercenary who served with him in the 1627 Saint-Martin-de-Ré expedition.

[23] The next day, they were attacked by a detachment from the New Model under Colonel Adrian Scrope; Dalbier was killed, Buckingham escaped to France and Rich taken prisoner to Windsor Castle.