Slavery in Britain existed long before the Roman occupation and until the Norman conquest in 1066, when the institution of slavery was gradually replaced by feudal serfdom and slaves were no longer recognised separately by English law.

During the Age of Discovery, British merchants were a driving force behind the Atlantic Slave Trade and profited significantly from slavery in British colonies oversees. However, no legislation was ever passed that legalised slavery in England. This was quite unique and different from other European countries like Portugal, France, the Netherlands that all passed comprehensive legislation to regulate slavery between the 15th and 17th century.

The lack of legal recognition brought confusion as to when British citizens brought their slaves, whom they had legally purchased in the colonies, to England. This uncertainty often resulted in legal struggles and contradicting court rulings.

One of the earliest cases of the matter was the Cartwright Case in 1569, when a man was observed savagely beating another man, which usually would have amounted to a battery charge, unless a defence could be mounted. The defendant argued that he had bought the other man as a slave and that he was his property and therefore could be dealt with as the defendant pleased. The court ruled against Cartwright and held that the man must be freed; according to the reports of John Rushworth, the court also held that "England was too pure an air for a slave to breathe in". The Cartwright Case became a key precedent for subsequent rulings, even though it was usually cited as imposing limits on the physical punishment of slaves, instead of assessing the legality of slavery in general. It took more than 200 years before the Cartwright Case was cited as authority that slavery was unlawful.

Another landmark ruling was the case Smith v Gould in 1705, in which Lord Chief Justice Sir John Holt ruled that "no man can have property in another" under Common Law. This decision was not without controversy, however, and sparked heavy criticism from other legal scholars. In 1729, the Attorney General, Philip Yorke, and the Solicitor General, Charles Talbot, of England issued the Yorke-Talbot opinion piece on slavery, arguing that the legal status of any enslaved individual did not change once they stepped foot in Britain; i.e. they would not automatically become free. This publication was drafted in response to the Smith v Gould decision, which the authors felt had opened up a discrepancy between the British colonies (where slavery was legally recognised) and the British motherland (where it wasn't).

This opinion piece was directly countered by Lord President Lord Henley in the 1763 case Shanley v Harvey, stating in relation to slavery that "as soon as a man sets foot on English ground he is free". However, this was a mere obiter dictum and therefore not legally binding to subsequent courts.

The most famous court trial involving slavery was perhaps Somerset v Stewart, that came before the King's Bench and its presiding Chief Justice, Lord Mansfield, in 1771.

James Somerset was an African slave, who had been bought by Charles Stewart in Boston, Massachussets. Stewart brought Somerset with him when he returned to England in 1769, but in late 1771 Somerset escaped his slave owner. Somerset was captured and imprisoned on board the ship Ann and Mary, which was bound to Jamaica, where Stewart intended to have his slave sold. Somerset's three godparents appealed before the Court of the King's Bench for a writ of habeas corpus, and Lord Mansfield granted a hearing for the following year. Lord Mansfield had originally pressed the parties to settle, but because slavery had become such a hotly contested issue neither side wanted to budge, especially as the case was taken up by the West India merchants, who wanted to know whether slaves were a safe investment, and by the abolitionist movement, pledging support to Somerset's case.

After having heard both sides, Lord Mansfield gave his judgement on 22 June 1772, ruling that Somerset was to be freed and that his imprisonment on board the slave ship was unlawful, stating "a foreigner cannot be imprisoned here on the authority of any law existing in his own country: the power of a master over his servant is different in all countries, more or less limited or extensive; the exercise of it therefore must always be regulated by the laws of the place where exercised."

Mansfield was careful to not comment on the slave laws in Britain's oversea possessions, knowing of course how dependent many colonies were on slavery, and instead solely focused on its legal state in England. He argued that "the state of slavery is of such a nature, that it is incapable of now being introduced by Courts of Justice upon mere reasoning or inferences from any principles, natural or political; it must take its rise from positive law;", effectively saying that as long as Parliament hadn't passed any legislation to codify slavery, it couldn't be recognised as a legal status by the courts.

Somerset v Stewart was a landmark decision that became legal precedent for all subsequent slave trials and was regularly cited as authority on the unlawfullness of slavery. However, it's still debated what kind of precedent this case actually set. Having been followed closely by the British press and throughout the British Empire, the trial sparked all kinds of reactions to its outcome from celebration to condemnation. Benjamin Franklin, who resided in London at the time of the trial, expressed criticism of Great Britain's hypocrisy regarding slavery, where Britons refused to recognise it at home, but encouraged it abroad.

The matter was not finally resolved though, and only when Parliament passed the Slavery Abolition Act 1833 was the institution of slavery abolished throughout the Empire.