In 1758 at the battle of St. Cas, Caswall was ‘wounded, and taken prisoner, being carried to St. Malo, he remained there four months in the most languishing condition, with both bones of his leg shattered by the ball. After great pain, and expense, he was brought to England, where his wound was healed.’
In 1761 Caswall was returned unopposed for Hertford on the interest of Nathaniel Brassey. On 29 July 1762 he wrote to Bute of his ‘hearty desire’ of being attached to him in Parliament, and begged him ‘to obtain of his Majesty a salary of five hundred a year, with the title of gentleman of the Horse to the Queen’
Only a handful of speeches by Caswall are recorded during his 25 years in Parliament. On 14 Mar. and 7 June 1774 he spoke on motions to clear the House. On 11 Dec. 1787, he explained that he had voted against Philip Francis as manager for the impeachment of Hastings, because Francis ‘had fought a duel with Mr. Hastings, and had consequently had a personal quarrel with him ... Mr. Caswall said he was a plain man and told a plain story’.
In September 1789 Caswall’s seat was vacated by his appointment to a commissionership of Excise. He died 24 Aug. 1802.
