John Thelwall, the son of a silk mercer, was born in 1764. He first became involved in politics when he campaigned on behalf of John Horne Tooke in the in the 1790 Westminster election. He also joined Tooke's Society for Constitutional Information. Two years later Thelwall helped Thomas Hardy to form the London Corresponding Society.
As well as campaigning for the vote, the strategy of the London Corresponding Society was to create links with other reforming groups in Britain. Thomas Hardy was appointed as treasurer and secretary of the organisation. The society passed a series of resolutions and after being printed on handbills, they were distributed to the public. These resolutions also included statements attacking the government's foreign policy. A petition was started and by May 1793, 6,000 members of the public had signed saying they supported the resolutions of the London Corresponding Society.
At the end of 1793 Thomas Muir and the supporters of parliamentary reform in Scotland began to organise a convention in Edinburgh. The Society sent two delegates Joseph Gerrald and Maurice Margarot, but the men and other leaders of the convention were arrested, tried for sedition. Several of the men, including Gerrald and Maragot, were sentenced to fourteen years transportation.
The reformers were determined not to be beaten and John Thelwall joined with Thomas Hardy and John Horne Tooke to organise another convention. When the authorities heard what was happening, the three men were arrested and committed to the Tower of London and charged with high treason. The men's trial began at the Old Bailey on 28th October, 1794. The prosecution, led by Lord Eldon, argued that the leaders of the London Corresponding Society were guilty of treason as they organised meetings where people were encouraged to disobey King and Parliament. However, the prosecution was unable to provide any evidence that Hardy and his co-defendants had attempted to do this and the jury returned a verdict of "Not Guilty".
The government continued to persecute John Thelwall and other supporters of parliamentary reform. Habeas Corpus was suspended in 1794, enabling the government to detain prisoners without trial. The Seditious Meetings Act made the organisation of parliamentary reform gatherings extremely difficult. At one public meeting addressed by Thelwall, on 26th October 1795, in Copenhagen Fields, it was claimed that over 150,000 people were in attendance. Although watched by government spies, Thelwall continued to give twice-weekly lectures in favour of political reform. These speeches were also published in Thelwall's journal, The Tribune. Thelwall also found time to write a book Rights of Nature that was published in 1796.
In later life Thelwall concentrated on journalism and in 1818 purchased the journal The Champion. The following year Thelwall was active in the protest meetings that erupted after the Peterloo Massacre.
John Thelwall died on 17th February 1834.