Although nowhere described as such, it seems likely that Maidstone was the son or nephew of Thomas Maidstone, who represented Middlesex in three Parliaments during the 1390s. The pair of them were clearly related, having strong connexions with Isleworth, where they both owned property. Four members of the Maidstone family, including Clement, the hagiographer, were educated at Winchester college, but the future shire knight was evidently not among them. He may well have held a clerkship in the royal Exchequer before becoming a teller there in September 1408. At all events, a clerk named Richard Maidstone witnessed a deed in the previous January for Philippa, wife of Sir John Tiptoft, who was then treasurer of the King’s household; and we know that the MP eventually acted as one of Tiptoft’s trustees, having no doubt established a position of trust over the years. At about this time Maidstone paid 3s.4d. to become a member of the prestigious fraternity of the Trinity and SS. Fabian and Sebastian at St. Botolph’s without Aldgate, perhaps because his duties obliged him to live in the City.
Maidstone took part in Henry V’s first expedition to France in August 1415, and was present as one of the earl of March’s contingent at the siege of Harfleur. In common with many of the besieging army, he was invalided back to England before the town fell, although he had time to take at least one prisoner, a Frenchman named Jean Fosseux, who, in January 1416, obtained a safe conduct to return home and negotiate a ransom.
Maidstone’s involvement in government at a county level began in December 1421 with his election as a knight of the shire for Middlesex. He had by then relinquished his tellership, perhaps in return for the post of controller of the Exchange in Lombard Street. His interests were, none the less, not confined to London. Besides sitting on a number of commissions in the home counties over the next 15 years, he attended at least six of the Middlesex parliamentary elections held between 1422 and 1442, and twice (in 1426 and 1427) stood surety for the shire knights returned. Later, in May 1434, he was instructed, as representative for Middlesex in the previous Parliament, to take oaths from the leading residents of the county that they would not assist persons disturbing the peace.
The summer of 1424 was spent by Maidstone in Ireland, where he acted as an attorney for two prominent London merchants, and it is possible that he remained there for some time. This would explain why no more is heard of him until he represented Middlesex for a second time in the Parliament of 1433, even though he had probably by then become involved in a dispute with the Cornish landowner, Sir John Arundell of Trerice. Not until December 1434, however, did the two parties offer mutual securities of £400 to accept the award of Sir William Cheyne, c.j.KB, as an umpire in the event of a disagreement between their chosen arbitrators. In the following February Sir John promised to pay Maidstone a sum of 200 marks which was duly delivered in three instalments. The cause of this disagreement is not recorded, but it may well have arisen over rival claims to land. According to the income tax assessments of 1436, Maidstone owned property in Cornwall, and Sir John could well have challenged his title. Maidstone’s other estates lay in the Isleworth and Twickenham area of Middlesex and Cheshunt in Hertfordshire; he and his wife also received rents of four marks a year from holdings in Erith and Lessness in Kent, which in November 1436 were confirmed to them for life under sureties of £100 by a London grocer. Altogether they enjoyed an estimated landed income of at least £36 a year, some of which probably came from the Dauntsey family estates.
Maidstone’s wife seems to have been a kinswoman—perhaps even the daughter—of Sir Walter Dauntsey, a landowner in the Midlands and south of England. Her death, shortly before November 1439, evidently came as a severe blow to Maidstone, and in the following December he made arrangements for a pilgrimage to the Holy Land. He himself was dead by 13 May 1443, since his daughter, Elizabeth, and her husband, Geoffrey Goodlake, had by then begun a lawsuit in Chancery for the recovery of part of her inheritance from one of Maidstone’s feoffees. They won their case, and in February 1444 were confirmed in possession of the property by Joan, the widow of Richard Maidstone, esquire, who was presumably Maidstone’s second wife or perhaps even his daughter-in-law.