Jonathan's new owner, the ship captain, and Sharp appeared, and the Lord Mayor, who knew the Sharp clan, declared Jonathan free. The ship's captain seized Jonathan, and Sharp clapped a hand on the Captain's shoulder and cried, "I charge you, in the name of the king, with an assault upon the person of Jonathan Strong, and all these are my witnesses." The Captain beat a speedy retreat, and Jonathan was free. His old owner challenged Sharp to a duel, but Granville ignored him.

It seemed incredible to Granville that men should be held as slaves. Aware that the Westminster Council had outlawed slavery in 1102, he immersed himself in reading law, searching for a way to establish a definitive legal ruling that would end slavery.

Granville Sharp had an interesting mind. His parents had educated his older brothers, but he had received very little education when he moved to London at fourteen and became an apprentice. Unenthusiastic about selling cloth, he left the draper's, and took a government job. Sacrificing sleep and his social life, he taught himself Hebrew and New Testament Greek. He experienced real happiness reading the Gospel in Greek, and he acquired a decided belief that the Gospel called for love and justice on earth.

Sharp noted the Common Law precedent of Cartwright (1569) which explicitly stated that slavery could not exist in England. This was confirmed in Shanley v Hervey (1762) when the court ruled, "As soon as a man puts foot on English ground, he is free: a Negro may maintain an action against his master for ill usage, and may have a Habeas Corpus, if restrained of his liberty." It was asserted again in Smith v Brown and Cooper (1765), when Chief Justice Holt ruled, "As soon as a negro comes into England, he becomes free: one may be a villein in England, but not a slave."

These rulings were ignored. Instead slave owners relied on the opinion (1729) of Crown officers Yorke and Talbot that slaves are the property of their owners in Britain as well as in the colonies. Sharp debunked the opinion, brilliantly showing in an essay published in 1769 that Yorke and Talbot had ignored the Council of Westminster, the decision in Cartwright, and Sir William Blackstone's influential Commentaries on the Laws of England, which asserted that slaves were free when they came to England.

Today it is a relatively easy thing to publish an opinion, and to be applauded by someone somewhere. It was not so easy then. Sharp's ideas challenged conventional wisdom and very rich people. He was condemned as a Christian evangelist. He remained undeterred.

In the late 1760s, Sharp made it his mission to find out when slaves were kidnapped in England and put on ships for the West Indies. Boarding the ships he brought the kidnapped former African slaves before magistrates who freed them. But the judges refrained from making a definitive ruling that would set a precedent against slavery.

In 1772, James Somerset (sometimes spelled Somersett) had been recaptured by his Boston, Massachusetts owner. He was lying in chains on a ship in London that was bound for Jamaica. Granville Sharp obtained a writ of habeas corpus from a judge, and the captain of the ship was ordered to produce Somerset before the court of King's Bench.

The suit was heard before William Murray, 1st Earl of Mansfield, the Chief Justice. Murray was the clear-headed judge who had established the fundamental principles of British mercantile law. When the case was brought before him he considered slavery a legal fact, and he was not eager to rule against it. Really he was not eager to make any ruling at all.

Though not a member of the bar, Granville had explored all the precedents, talked with legal authorities, and developed the legal case for freeing Somerset, which he described in an essay (On the Injustice and dangerous Tendency of tolerating Slavery), and had delivered to Mansfield. The representing barristers made Granville's arguments, and Judge Mansfield made a 180° turn. He ruled that slavery was "odious", that James Somerset's servitude was not supported by law, and that he must be freed.

Though it was not the exact ruling Sharp had looked for, the public thought it was, and it was used to free slaves brought to Britain. But slavery in the West Indies continued in all its misery. For the next fifteen years, Sharp wrote and campaigned against slavery, but he laboured almost alone.

He was also absorbed in advocating parliamentary reform in Britain and an independent legislature in Ireland, in the family's musical enterprises, and in defending the rights of American colonists. Thousands of copies of his no taxation without representation pamphlets were published in Boston, Philadelphia, and New York. One wonders how he found time to do his job, and in fact he resigned his job in protest at the war in America, writing the government, "I cannot return to my ordnance duty whilst a bloody war is carried on, unjustly as I conceive, against my fellow-subjects." (His brothers rushed to his rescue, writing him that they supported his principles, and hoped he would live with them, for "the happiness of being together." And so they all did for the rest of their lives.)

Despite Granville's best efforts, the anti-slavery movement was not making headway. With very few exceptions people in Britain did not think about the slave trade. When they did, they considered it to be the foundation of their commerce and the source of their wealth. It was believed that ending slavery would cause a collapse of the economy. Around the time that James Ramsay was returning to Britain, Granville began to help Africans who had been freed to return to Africa by establishing their own country, Sierra Leone. The effort failed. To those who cared it appeared that the dream of freedom was dying.

It was James Ramsay, without hope or home or job, who would recharge the cells of the anti-slavery movement. He was about to receive the indispensable help and inspiration of Margaret, Lady Middleton.