Handcock, whose uncle William, created Baron Castlemaine in 1812, was governor and sole proprietor of Athlone, served in alternate years from 1816 to 1826 as sovereign and vice-sovereign of the family controlled corporation on a salary of £100 per year, a position which had been held since 1798 by his father, who succeeded to the barony in 1839.
Handcock signed the Irish landed proprietors’ petition against Catholic relief in February, voted thus, 6 Mar. 1827, 12 May 1828, and brought up hostile petitions, 28 Apr., 1 May 1828.
At the 1830 general election he was returned after a token contest with an outsider.
At the 1832 general election he stood unsuccessfully as a Conservative for Athlone and he was defeated in Westmeath in 1837. Following his succession in 1840 as 3rd Baron Castlemaine he pressed his claims to the Irish representative peerage, but finding that it had ‘been arranged that ... Lord Caledon should come in’ on the first vacancy, he informed Sir Robert Peel, 6 Mar. 1841, that he was ‘not willing to create any division’ and would ‘withdraw’, adding that ‘in doing so, I hope I shall be considered on the next vacancy, trusting that past services and that my endeavours to recover what we have at present lost in Westmeath and Athlone, will not be forgotten’.
