Thomas Spence a schoolteacher from Newcastle-upon-Tyne arrived in London in December 1792. Soon after arriving he was arrested for selling Rights of Man by Tom Paine. For the next twenty years of his life Spence spent long periods in prison for selling Radical books, pamphlets, newspapers and broadsheets.
By the early 1800s Thomas Spence had established himself as the unofficial leader of those Radicals who advocated revolution. Spence did not believe in a centralized radical body and instead encouraged the formation of small groups that could meet in local public houses. At these meetings Spence argued that "if all the land in Britain was shared out equally, there would be enough to give every man, woman and child seven acres each". At night the men walked the streets and chalked on the walls slogans such as "Spence's Plan and Full Bellies" and "The Land is the People's Farm". In 1800 and 1801 the authorities believed that Spence and his followers were responsible for bread riots in London. However, they did not have enough evidence to arrest them.
Thomas Spence died in September 1814. He was buried by "forty disciples" who pledged that they would keep his ideas alive. They did this by forming the Society of Spencean Philanthropists. The men met in small groups all over London. These meetings mainly took place in public houses and they discussed the best way of achieving an equal society. Places used included the Mulberry Tree in Moorfields, the Carlisle in Shoreditch, the Cock in Soho, the Pineapple in Lambeth, the White Lion in Camden, the Horse and Groom in Marylebone and the Nag's Head in Carnaby Market.
The government became very concerned about this group that they employed a spy, John Castle, to join the Spenceans and report on their activities. In October 1816 Castle reported to John Stafford, supervisor of Home Office spies, that the Spenceans were planning to overthrow the British government.
On 2nd December 1816, the Spencean group organised a mass meeting at Spa Fields, Islington. The speakers at the meeting included Henry 'Orator' Hunt and James Watson. The magistrates decided to disperse the meeting and while Stafford and eighty police officers were doing this, one of the men, Joseph Rhodes was stabbed. The four leaders of the Spenceans, James Watson, Arthur Thistlewood, Thomas Preston and John Hopper were arrested and charged with high treason.
James Watson was the first to be tried. However, the main prosecution witness was the government spy, John Castle. The defence council was able to show that Castle had a criminal record and that his testimony was unreliable. The jury concluded that Castle was an agent provocateur (a person employed to incite suspected people to some open action that will make them liable to punishment) and refused to convict Watson. As the case against Watson had failed, it was decided to release the other three men who were due to be tried for the same offence.