Byng, who followed his father into the army, joined Brooks’s Club, 21 May 1826, in accordance with his family’s Whig politics. When his father was appointed to the Irish command in 1828 he became one of his aides-de-camp, and early the next year he married a daughter of Lord Anglesey, the pro-Catholic viceroy, who had just been recalled in disgrace by the Wellington ministry. Within days reports appeared in the Irish press to the effect that the couple had already separated. Lady Agnes was said to have refused to consummate the marriage and to have confessed to a pre-marital affair with Lord Errol, so provoking Byng to desert her. It was also rumoured that Anglesey had connived at his daughter’s intrigue in order to facilitate his own adultery with Lady Errol, the illegitimate daughter of the duke of Clarence. The stories were traced to a letter written by Gerard Callaghan* to a fellow Brunswicker. The Byngs brought an action for defamation and libel against him and the case, which had obvious political overtones, excited considerable interest. Yet when it came on at Cork assizes, 28 Aug. 1829, it was immediately dropped, for Callaghan apologized, declared that he had been duped into circulating stories ‘which he now believed to be utterly false’ and disclaimed any political motive. Daniel O’Connell*, who had been engaged as counsel for the Byngs, thought his senior John Doherty*, the Irish solicitor-general, had ‘botched’ the case and afforded Callaghan ‘a decided triumph’.
At the general election of 1830 Byng was returned by his father-in-law for Milborne Port. Ministers duly listed him among their ‘foes’, but he was absent from the crucial division on the civil list, 15 Nov. 1830. On 14 Feb. 1831 Anglesey, reinstated as viceroy by Lord Grey’s ministry, asked him to vacate his seat for the Irish barrister Richard Sheil*, whom ministers were keen to bring in, with the hope of a free seat for Cashel. He accepted a place in Anglesey’s household and vacated as soon as his work on the Wexford election committee was complete, 21 Feb. The Irish secretary Smith Stanley hoped that Cashel could be procured for Byng, as he ‘seems annoyed at going out, and I find he has given up his Irish appointment’. The negotiation for Cashel fell through, but within three weeks he was returned again for Milborne Port, replacing the other Member, Sturges Bourne, who was unable to support the ministerial reform bill.
Milborne Port was disfranchised by the Reform Act and Byng did not find another seat until 1834, when he was appointed, to the derision of some observers, to the first of a succession of minor offices in Liberal governments.
