Irby’s father did not follow other members of his family by pursuing a legal career, but dabbled in trade, becoming a member of the Levant Company; he died in 1610, when Irby was only five years old.1T.K. Rabb, Enterprise and Empire, 321. During Irby’s long minority his estates were administered by his grandfather, Anthony Irby*, whose puritan sympathies he shared.2Lincs. N and Q, xiii. 81. Knighted during a visit to Theobalds in 1624, Irby inherited extensive estates the following year on his grandfather’s death. There were estimated to be worth over £4,000 a year, and included a house at Boston.3Her. and Gen. ii. 122; Irby, i. 37. Named as a commissioner for the Forced Loan in 1627, he nonetheless refused to contribute to the levy, for which offence he was summoned before the Privy Council.4APC, 1627, p. 142; SP 16/56/39; R. Cust, Forced Loan, 172, 226, 311, 334. There he presumably managed to make his peace, since, unlike other unco-operative commissioners, he was not imprisoned but ordered to remain in attendance.5C. Holmes, Seventeenth Cent. Lincs, 107-8. He appeared in a somewhat different light when he was summoned again the following year, after an independent inquiry revealed that he had taken advantage of a widow’s ignorance to buy her land at an undervalue. He flatly refused to pay the suggested compensation of £50 on the grounds that this would call in question his title to other parts of his estate, and insisted on a trial at law.6APC, 1627-8, p. 441; 1628-9, p. 221; CSP Dom. 1627-8, p. 552; 1628-9, p. 370.
Irby contested the 1628 election for Boston, his opponent being Richard Oakeley*, the nominee of the bishop of Lincoln. Although narrowly outvoted on the corporation, he obtained 67 votes from the freemen, whose right to participate was uncertain. On petition he established the wider franchise, but it took more than seven weeks for the Commons to rule that he had won the seat.7CD 1628, iii. 324; J.K. Gruenfelder, ‘Boston’s Early Stuart Elections’, Lincs. Hist. and Arch. xiii. 47-49. Once at Westminster, he joined his brother-in-law, Sir John Wray*, who had been returned for the county. Irby played no recorded part in the remainder of the first session, and was appointed to just two committees in the second. One was for a private estate bill concerning (Sir) Arnold Herbert* (21 Feb. 1629) and the other was for a bill to prevent simony in university colleges (23 February).8CJ, i. 932a, b.
During his shrievalty in 1637 Irby emerged as one of the leaders of resistance to Ship Money in the county. He aroused opposition by altering the assessments to help poorer areas, ending up some £2,662 in arrears. The Council believed that his tardiness in paying over the money was deliberate, and he was threatened with a Star Chamber prosecution.9CSP Dom. 1637-8, pp. 138, 211-12, 526, 589; 1639, pp. 25, 49, 371, 466; 1639-40, p. 300; Holmes, 131-3. He was re-elected for Boston at both elections in 1640, fought for Parliament in the Civil War, held office throughout the Interregnum, and as a committed Presbyterian was a supporter of exclusion after the Restoration.10M.F. Keeler, Long Parl. 230-1; Holmes, 221, 235. Having made his will, dated 23 July 1680, Irby died on 2 Jan. 1682, and was buried at St. Margaret’s, Westminster.11PROB 11/383, f. 107v; Thompson, 395.