To make a new law to abolish or ban something requires an Act of Parliament. The proposal to make this change is called a Bill. It has to go through many stages before it becomes an Act that must be obeyed. The Bill to Abolish the Slave Trade took much longer than most - 15 years - as it was opposed by so many.
The Bill was first presented in April 1792 by William Wilberforce. He was the Member of Parliament for Hull and a close friend of Thomas Clarkson. The Abolitionist Society's local campaigns were then delivering hundreds of petitions to Parliament.
All was going well until the Member of Parliament for Edinburgh - Lord Henry Dundas - proposed an 'amendment' (a small change).
This was the insertion of the word 'gradual' into the wording of the final Act. He claimed the merchants in the trade needed time to find other employment for their ships and crews.
He wanted nothing to become compulsory until 1796. Dundas was very influential and so this amendment was accepted. In reality, the amendment was used every year to block Wilberforce's attempts to reintroduce his Bill.
During this time the voters were scared away from supporting the Abolitionists by claims that they were dangerous 'radicals', like the French revolutionaries who had killed their king (1789) and nobles and who were now making sweeping changes to their society.
It took a long time for this fear to subside. In January 1807 Wilberforce finally got his Bill heard again. This time it had the support of key members of the government and the new Irish MPs.
The Bill was passed (23 February) with a resounding 'three distinct and universal cheers'. It was a highly emotional scene in British Parliamentary history. A month later the Bill received the Royal Assent and became law.
It was, of course, not binding on the other slaving nations. Africans were still carried off by illegal traders for another 50 years. Nor did it dismantle slavery on the plantations. The Abolitionists' great hope that the institution itself would soon crumble after the trade was stopped did not materialise.
It would take a further 30 years of bitter campaigning by Wilberforce and Clarkson's new organisation - the Anti-Slavery Society - to achieve the 'emancipation' of all slaves in the British colonies, and only after 20 million pounds in compensation was paid to the owners. The former slaves got nothing.