[2] He is known to have begun publishing anonymous attacks on the bishops about the time of the opening of the Long Parliament, together with some pungent verse satires, like Lambeth Fayre and Articles of High Treason against Cheapside Cross, 1642.
[4] The tract created a great stir, and a small sect arose known as "Soul Sleepers", who adopted Overton's doctrine in a slightly modified form.
[5] On 26 August 1644, the House of Commons, on the petition of the Stationers' Company, ordered that the authors, printers, and publishers of the pamphlets against the immortality of the soul and concerning divorce should be diligently inquired for, thus coupling Overton with Milton as the most dangerous of heretics.
[6] Daniel Featley in the Dippers Dipt and Thomas Edwards (1599–1647) in Gangræn both denounced the unknown author, the latter asserting that Clement Wrighter "had a great hand in the book".
He was also one of those who presented to Fairfax on 28 December 1648 the Plea for Common Right and Freedom, a protest against the alterations made by the council of the army in Lilburne's draft of the Agreement of the People.
[15] In conjunction with three fellow-prisoners he issued, on 1 May 1649, the Agreement of the Free People of England, followed on 14 April by a pamphlet denying the charge that they sought to overthrow property and social order.
[16] On his own account he published on 2 July 1649 a Defiance to the government, in the form of a letter addressed to the citizens usually meeting at the Whalebone in Lothbury, behind the Royal Exchange, a place which was the headquarters of the London Levellers.
In September 1654 Overton proposed to turn spy, and so offered his services to Thurloe for the discovery of plots against the Lord Protector's government.