The Leigh family originated in Shropshire, owing the rise in its fortunes to the successful career of the prosperous merchant Sir Thomas Leigh (d.1571), who became lord mayor of London and left extensive estates to his three sons. The second son, also Thomas, inherited Stoneleigh in Warwickshire. Stoneleigh was the largest house in the county and was assessed at 70 hearths in 1660.
Leigh was for the most part a loyal supporter of the king during the civil wars and owed his elevation to the peerage to service in the king’s cause. Yet he maintained good relations with some of his neighbours of the other party and was the beneficiary of assistance by at least two major parliamentarian figures, Robert Greville†, Baron Brooke, and Basil Feilding, 2nd earl of Denbigh. Leigh attended the Oxford Parliament but in 1646, following the king’s defeat, he petitioned to compound, pleading that he had been compelled to open his gates to the king in 1642 and that he had never been ‘in arms nor assisted the king with men, horses or money’. This was demonstrably false: Leigh had at one point been taken prisoner while in command of a company of royalist horse and he had contributed funds for the king’s coffers in return for his peerage. The assessors evidently paid little heed to his account. He was said to have ‘suffered much’ at the hands of the grand commissioner and was forced to pay a substantial composition, which was increased in 1648 after it was determined that Leigh had underestimated his income by approximately £1,000.
Leigh was watched carefully during the Interregnum and was arrested as a precaution during the rising led by George Booth, later Baron Delamer, but he does not appear to have been an active royalist plotter and he was not incarcerated for long. At the Restoration, he was among the first of the royalists to gather in London, arriving in the capital on 17 May, but in common with the majority of those in possession of Civil War peerages he delayed taking his seat in the House. He first attended on 4 June 1660, after which he was present on a third of all sitting days. He appears to have been an inactive Member. He was named to no committees and on 7 Aug. he was given a month’s leave to go to Bath on account of his health.
He did not sit again until the following year, covering his absence in the second session of the Convention by registering his proxy with his kinsman Thomas Wriothesley, 4th earl of Southampton, on 10 November.
Leigh became guardian to his grandson, another Thomas Leigh, later 2nd Baron Leigh, in 1666, following the death of his son and heir four years previously. By this time, his financial situation appears to have deteriorated further. Roger Boyle‡, earl of Orrery [I], appealed to Edward Hyde, earl of Clarendon, to encourage Leigh ‘to clear his grandchild’s fortune of its encumbrances’.
Leigh was again said to be suffering from poor health in January 1672.
