John Venn, 1586-1650
Militant Puritan and ally of Isaac Penington in London, he sat on the High Court of Justice and signed the King's death warrant.
Born into a yeoman family of Somerset, John Venn was apprenticed to the Merchant Taylors' Company in London in 1602 and established himself as a successful merchant trading in wool and silk during the 1620s. He became a founding member of the Massachusetts Bay Company and was appointed one of its governors in 1629. A devout Puritan, Venn and his wife Mary were members of the congregation of All Hallows in Bread Street where he was chosen as a churchwarden in 1631.
Venn was also active in the London militia. He joined the Artillery Garden in 1614 and had attained the rank of lieutenant-colonel in the Yellow regiment of the London Trained Bands by 1642. It was Venn's association with the militia that first brought him to prominence in London politics when he campaigned in a disputed Artillery Garden election in 1631. By 1638, he was a member of the Common Council of London and active on several influential committees.
Venn emerged as a leader of the Puritan militants of London during 1640-1. He helped organise the petition sent to King Charles at York in September 1640 calling for a new Parliament, and the Root and Branch Petition for religious reform in December. In co-operation with his colleague Isaac Penington, Venn led the campaign demanding the prosecution of the Earl of Strafford, and mobilised demonstrations against the power of Archbishop Laud and the supposed influence of the Catholics.

After the death of the London MP Matthew Cradock in June 1641, Venn was elected to the Long Parliament in his place. He was accused of mobilising apprentice riots at Westminster during Parliament's debates on the Grand Remonstrance in order to intimidate MPs opposed to the Remonstrance. During the summer of 1642, he was active in the campaign to remove the royalist Lord Mayor of London Sir Richard Gurney, and to secure the election of Isaac Penington in his place. King Charles denounced both Venn and Penington as traitors for stirring up London against him, and declared that they would never be pardoned.
With civil war inevitable, Venn raised subscriptions from the citizens of London to support Parliament's war effort. When hostilities began, he was appointed a colonel of foot in the army of the Earl of Essex. Shortly after the battle of Edgehill in October 1642, Venn was appointed governor of Windsor Castle. He defied Prince Rupert's summons to surrender the castle in November 1642. Venn remained at Windsor until 1645 when he resigned from the governorship under the Self-Denying Ordinance. Upon his return to London, Venn became a leading Independent. He was appointed to the important Militia Committee following the failure of the Presbyterian faction to gain control of the London militia in 1647.
In January 1649, Venn was appointed a commissioner of the High Court of Justice which conducted the trial of King Charles, and was one of the signatories of the King's death warrant. After the establishment of the Commonwealth, Venn was active on many parliamentary committees, and profited from the sale of Church and Royalist lands.
Venn died suddenly in June 1650. The rumour that he committed suicide was probably false.
Sources:
Keith Lindley, John Venn, Oxford DNB, 2004