The National Archives of the UK website states, regarding the British Parliament Slavery Abolition Act of 1807, "Despite opposition from a variety of people with vested interests, the abolitionists and their supporters persisted. In 1806, Lord Grenville made a passionate speech arguing that the trade was 'contrary to the principles of justice, humanity and sound policy'. When the bill to abolish the slave trade was finally voted upon, there was a majority of 41 votes to 20 in the Lords and a majority of 114 to 15 in the Commons.
On 25 March 1807, the Abolition of the Slave Trade Act entered the statute books. Nevertheless, although the Act made it illegal to engage in the slave trade throughout the British colonies, trafficking between the Caribbean islands continued, regardless, until 1811."