Swinarton was probably descended from the Staffordshire family of the same name, which had first produced a knight of the shire in 1322.
In 1604 Swinarton was presumably returned for East Grinstead on the interest of lord treasurer Dorset (Thomas Sackville†), with whom he had had frequent financial dealings. He left no mark at all on the records of the first session, but was later named to 16 committees, mostly concerned with London. Towards the end of 1604 he formed a syndicate under the patronage of Henry Howard, 1st earl of Northampton, which repeatedly but unsuccessfully applied for the great farm of the customs.
In October 1605, shortly before the opening of the second session, Swinarton was appointed by the London Court of Aldermen to a committee to oversee the City’s business in Parliament. On 13 Feb. 1606 he was included in the City delegation sent to lobby Parliament for a bill that the corporation had drafted about the coal trade. During the session he was subsequently included in committees appointed by the corporation to consider both the bill concerning coal and another about Leadenhall market.
In the third session Swinarton was instructed to attend a conference with the Lords on the Union with Scotland (25 Nov. 1606), and was again appointed to consider bills for the capital’s housing (8 Dec.) and water supply (1 May 1607), as well as the bill for securing its corporation and companies in possession of their lands (4 May). He was also among those added to the committee for the bill to confirm Southampton’s charter on 11 May, a measure designed to stop Londoners trading in the town and consequently bitterly opposed by the City.
Swinarton still hoped to wrest the great farm away from his rivals, and by early 1607 the prize appeared to be within his grasp. Chamberlain reported that Northampton was ‘further in grace than ever, ... whereby it is thought he hath overthrown the earl of Salisbury’s patentees of the customs, and a new patent is making for Sir John Swinarton and his associates, who they say offers £100,000 for a fine and £4,000 more yearly rent than is now paid’.
In the same year the Merchant Taylors made use of Swinarton’s connections in preparing for the entertainment of the king at their Hall during his father’s mastership. He was asked to confer with Ben Jonson about a speech of welcome and suitable ‘music and other inventions’.
Swinarton was named to four committees in the fourth session, including one for the lands of the Salters’ and Brewers’ Companies (20 Feb. 1610).
Swinarton served as lord mayor of London in 1611-12, when he entertained the Elector Palatine, opened the sluices of the New River, and, again in partnership with Cranfield, continued his campaign against the customs farmers, whom he accused of defrauding the Crown of £70,000 a year.
Swinarton died on 8 Dec. 1616, ‘not altogether’, according to Chamberlain, ‘so great or rich a man as he was held, and made show of’.
