Author of the History of Independency, which as a project with several editions included also his Anarchia Anglicana, he was a strong opponent of religious factionalism, and was imprisoned in the Tower of London, where he died without being brought to trial.
He was advocate to the court-martial which condemned Robert Yeomans and George Bouchier (Bowyer) for seeking to betray Bristol to Prince Rupert, and was at first a strong supporter of Colonel Nathaniel Fiennes as governor of that city.
After the surrender of Bristol by Fiennes to Prince Rupert, Walker became his most bitter enemy, co-operated with William Prynne in publishing pamphlets against him, and finally secured his condemnation by a court-martial.
In December 1648 Walker was one of the members who voted the king's concessions sufficient ground for an agreement with him, and was consequently expelled from the house by Pride's Purge.
Walker's major work was a composite,[2] consisting of: The History of Independency and Anarchia Anglicana were published under the pseudonym of Theodorus Verax.
An abridgment in Latin of part of the History of Independency, entitled Historia Independentiae, is included in Sylloge Variorum Tractatuum, 1649, and in Metamorphosis Anglorum, 1653.