John Castle was born in Yorkshire in about 1785. Castle moved to London where he found work in a brothel run by Mother Thoms in King Street Soho. In 1812 Castle and his friend, Daniel Davis, were arrested for forging bank notes. The charges against Castle were dropped when he agreed to give evidence against Davis. As a result of Castle's evidence in court, Daniel Davies was executed.
In 1816 Castle was working as a whitesmith when he met James Watson, one of the leaders of the Spencean Philanthropists, a group inspired by the ideas of Thomas Spence. Soon afterwards John Castle became a member of the Spenceans.
William Salmon, a police officer at Bow Street, knew of Castle's police record and when discovered that he had become a Spencean he told John Stafford, the Chief Clerk at Bow Street, and Home Office spymaster. Stafford decided to recruit Castle as a spy. After a combination of threats and promises, Castle agreed to provide Stafford information on the activities of the Spenceans.
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. John Castle was the main prosecution witness. However, the defence council was able to show that Castle had a long 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.
I told him he did not deal candidly with me, and that I knew he had not disclosed all he knew. He declared nobody could say anything against him, for he detested violence and bloodshed. When people had too much drink they talked of that had better not been mentioned. He said he knew he was liable to be brought to Bow Street and publicly examined. He with others had suffered a great deal from distress and that he did not much care for his life and a man could only die once.
Mr. Stafford introduced me to Mr. Beckett the Under-Secretary (at the Home Office), who did assure me my safety on condition that I told the truth, which was a great ease to my mind, and from that moment I entered into confidential communication with Mr. Stafford. I shall get away with it if I can but if I should be taken I expect to be protected. I know I run great risk of assassination but I am determined to go through with it and report everything.
Question: How long have you had that coat on?
John Castle: A month or six weeks.
Question: Did Mr. Stafford order it for you?
John Castle: No.
Question: Who did?
John Castle: I ordered it at the clothes shop.
Question: Mr. Stafford. Question: Ever since your arrest you have been supported by him?
John Castle: I do not know who paid the expenses; the clothes were purchased by Mr. Stafford and given to me.
Question: Have you had any pocket money from Mr. Stafford?
John Castle: I have.
Question: Who furnished the money for your wife's going down to Yorkshire?
John Castle: Mr. Stafford.
It is impossible to know how far the higher members of the Government are involved in the guilt of their infernal agents. But this much is known, that so soon as the whole nation lifted up its voice for parliamentary reform, spies went forth. These were selected from the most worthless and infamous of mankind, and dispersed among the multitude of famished and illiterate labourers. It was their business to find victims, no matter whether right or wrong.