Cust, a veteran of Waterloo, had represented the venal borough of Honiton as a treasury nominee since 1818, and came in there unopposed at the general election of 1820 after the home secretary Lord Sidmouth intervened in his favour.
He declined a requisition to contest Grantham and was unopposed at Clitheroe at the 1830 general election.
Cust left Parliament at the dissolution in 1832 and apparently did not seek another seat. He remained on army half-pay until 1846. Thrice married, on the last occasion at the age of 69, he died in September 1873. By his will, dated 6 Apr. 1872 and proved, 17 Oct. 1873, he bequeathed £4,000 each to his two surviving children, left his real estate to his son John Francis (1825-1903), a former lieutenant-colonel in the Grenadier Guards, and his personal effects to his daughter. Another son Horace (1829-1854), was killed in the battle of Alma in the Crimea.
