Winning Catholic Emancipation in 1829 had been a personal triumph for O'Connell. From this time onwards, his supporters referred to him as the ‘Liberator’. His subsequent election to the British Parliament, and that of some of his supporters, changed the face not only of Irish, but also British, politics as they demonstrated that their interests extended beyond matters concerning Ireland. The reform of Parliament and the abolition of slavery were the two most pressing political debates, which not only engrossed Parliament, but aroused considerable public interest. O'Connell supported both and the latter brought him into contact with the leading anti-slavers of the day. His oratorical skills, his passion and intrepidness, meant that he quickly emerged as one of the movement's most influential and energetic advocates.

Following his election to the British Parliament, O'Connell dedicated himself to two issues: repeal of the Act of Union and anti-slavery. In Britain, anti-slavery brought him into contact with people who bitterly opposed his campaign for repeal, whilst in America, it brought him into contact with people who supported repeal but opposed abolition. Shortly after moving to London to take his seat, O'Connell met with anti-slavery leaders in Britain and in Westminster. From the outset, O'Connell made it clear that he intended to use his place in Parliament to fight for slave emancipation. The Cork Anti-Slavery Society had requested him to submit a petition on their behalf. No other Irish MP would agree to take it.