The son of a clergyman and a native of county Wexford, Jacob was of Quaker origins and ‘Orange lineage’. While still a minor, he married the daughter of an active and influential local magistrate and ‘zealous loyalist’, who served as high sheriff of the county.
A ‘gentleman of great respectability’, Jacob joined the Catholic Association and came to prominence in November 1829 when he allied himself with a Church reform movement which had recently been started in Cork by the evangelical earl of Mountcashel.
In February 1834 Jacob was brought forward for a vacancy at Dungarvan by Daniel O’Connell, who had faith in the integrity of this ‘plain and honest man’, and described Jacob’s return as ‘one of the most pleasing events in my life’.
Although Conservative opponents considered that as a Protestant Jacob had been ‘a much more dangerous foe’ to the Protestant interest than a Catholic Member, he stood down before the 1835 general election when it was claimed that, ‘having squandered almost all his fortune on elections’, he had been ‘forced to resign’ to make way for O’Connell’s favoured candidate.
Belligerent and possessed of a bullying manner, Jacob was noted as a duellist.
Jacob’s aggressive temperament led to his embroilment in a ruinous legal dispute with a fellow repealer named Christopher Eiffe, the managing director of the Caledonian Insurance office in Dublin and auditor for the lord mayor of Dublin. In May 1837 Jacob published a letter in which he imputed Eiffe’s conduct and character. Although he subsequently retracted the accusations, he was successfully prosecuted for libel. Jacob fled to England but in 1840 was remanded for debt. Unable to pay the damages, and in debt to his former commander, John Ross, for £1,200, he languished in the Queen’s Bench prison, London, until discharged by the insolvent debtors’ court in January 1844.
