The final version of the Agreement of the People was published in May during their imprisonment, but the suppression of the army Levellers at Burford by Fairfax and Cromwell in the same month effectively ended the movement's political viability. The Leveller leaders were released from prison in November following Lilburne's trial and acquittal. After the establishment of Cromwell's Protectorate, Overton became involved in Leveller-Royalist conspiracies against the government and joined Edward Sexby at Amsterdam in February The plots came to nothing, however, and Overton returned to England, where he published a revised version of his treatise Man Wholly Mortal.
Although several political tracts and pamphlets are attributed to Overton during the Protectorate, details of his later life are uncertain. Overton was one of the Levellers who, during the English Civil War, were among the very first to articulate the early ideas of liberalism. In this essay, he argues that every individual owns himself and so has rights to life, liberty, and property.
To every individual in nature is given an individual property by nature not to be invaded or usurped by any. For every one, as he is himself, so he has a self-propriety, else could he not be himself; and of this no second may presume to deprive any of without manifest violation and affront to the very principles of nature and of the rules of equity and justice between man and man. Mine and thine cannot be, except this be.
And from this fountain or root all just human powers take their original — not immediately from God as kings usually plead their prerogative but mediately by the hand of nature, as from the represented to the representers. For originally God has implanted them in the creature, and from the creature those powers immediately proceed and no further.
And no more may be communicated than stands for the better being, weal, or safety thereof. He that gives more, sins against his own flesh; and he that takes more is thief and robber to his kind — every man by nature being a king, priest and prophet in his own natural circuit and compass, whereof no second may partake but by deputation, commission, and free consent from him whose natural right and freedom it is….
And sir let it not seem strange unto you that we are thus bold with you for our own. For by nature we are the sons of Adam, and from him have legitimately derived a natural propriety, right and freedom, which only we require. And how in equity you can deny us we cannot see. It is but the just rights and prerogative of mankind whereunto the people of England are heirs apparent as well as other nations which we desire; and sure you will not deny it us, that we may be men and live like men.
If you do, it will be as little safe for yourselves and posterity as for us and our posterity. If by your present policy and abused might, you chance to ward it from yourselves in particular, yet your posterity — do what you can — will be liable to the hazard thereof. And therefore sir we desire your help for your own sakes as well as for ourselves, chiefly for the removal of two most insufferable evils daily encroaching and increasing upon us, portending and threatening inevitable destruction and confusion of yourselves, of us, and of all our posterities: For the first, namely the exorbitances of the Lords: And page 46, branches 1, 2 and 5, in these words: That no man be taken or imprisoned, but per legem terrae , that is by the common law, statute law, or custom of England.
For these words, per legem terrae being towards the end of this chapter, do refer to all the pretended matters in this chapter; and this has the first place, because the liberty of a man's person is more precious to him than all the rest that follow; and therefore it is great reason that he should by law be relieved therein, if he be wronged, as hereafter shall be showed. No man shall be disseised, that is, put out of seisin, or dispossessed of his freehold that is, lands or livelihood or of his liberties or free customs that is, of such franchises and freedoms, and free customs, as belong to him by his free birthright unless it be by the lawful judgement, that is verdict of his equals that is of men of his own condition or by the law of the land that is, to speak it once for all by the due course and processes of law.
No man shall be in any sort destroyed unless it be by the verdict of his equals or according to the law of the land. And, chapter 29 of Magna Carta , it is said, 'secundum legem et consuetudinem Angliae' after the law and custom of England 'non regis Angliae' not of the king of England — 'lest it might be thought to bind the king only, nec populi Angliae , not the people of England; 'but that the law might tend to all, it is said, per legem terra , by the law of the land'.
By colour of which act, shaking this fundamental law, it is not credible says he what horrible oppressions and exactions — to the undoing of infinite numbers of people — were committed by Sir Richard Empson, Knight, and Edmund Dudley, being Justices of the Peace through England; and upon this unjust and injurious act as commonly in the like cases it falls out a new office was erected, and they made Masters of the King's Forfeitures.
But at the parliament held in 1 Hen. And to this end the judgement upon Simon de Beresford, a commoner, in the fourth year of Edward III's reign, is an excellent precedent for these times as is to be seen upon record in the Tower in the second roll of parliament held the same year of the said king and delivered into the Chancery by Henry de Edenston, Clerk of the Parliament — for that the said Simon de Beresford having counselled, aided and assisted Roger de Mortimer to the murder of the father of the said king, the king commanded the earls and barons in the said parliament assembled to give right and lawful judgement unto the said Simon de Beresford.
But the earls, barons and peers came before the lord the king in the same parliament and said with one voice that the aforesaid Simon was not their peer or equal, wherefore they were not bound to judge him as a peer of the land. Yet notwithstanding all this, the earls, barons and peers being over-swayed by the king did award and adjudge as judges of parliament, by the assent of the king in the said parliament that the said Simon as a traitor and enemy of the realm should be hanged and drawn; and execution accordingly was done.
But as by the said roll appears, it was by full parliament condemned and adjudged as illegal, and as a precedent not to be drawn into example. The words of the said roll are these, viz. And it is assented and agreed by our lord the king and all the grandees in full parliament: Agrees with the Record.
But notwithstanding all this our lords in parliament take upon them as judges in parliament to pass judgement and sentence even of themselves upon the commoners which are not their peers — and that to fining, imprisonment, etc. And this doth not only content them, but they even send forth their armed men, and beset, invade, assault their houses and persons in a warlike manner and take what plunder they please, before so much as any of their pretended, illegal warrants be showed — as was lately upon 11 August perpetrated against me and mine, which was more than the king himself by his legal prerogative ever could do.
For neither by verbal commands or commissions under the Great Seal of England could he ever give any lawful authority to any general, captain or person whatsoever, without legal trial and conviction, forcibly to assault, rob, spoil or imprison any of the free commoners of England. And in case any free commoner by such his illegal commissions, orders or warrants, before they be lawfully convicted, should be assaulted, spoiled, plundered, imprisoned, etc.
And if the king himself have not this arbitrary power, much less may his peers or companions, the lords, over the free commons of England.
And therefore notwithstanding such illegal censures and warrants either of king or of Lords no legal conviction being made the persons invaded and assaulted by such open force of arms may lawfully arm themselves, fortify their houses which are their castles in the judgement of the law against them; yea, disarm, beat, wound, repress and kill them in their just necessary defence of their own persons, houses, goods, wives and families, and not be guilty of the least offence — as is expressly resolved by the Statute of 21 Edw.
And therefore sir as even by nature and by the law of the land I was bound, I denied subjection to these lords and their arbitrary creatures thus by open force invading and assaulting my house, person, etc.
But and if they had brought and shown a thousand such warrants, they had all been illegal, antimagisterial and void in this case; for they have no legal power in that kind, no more than the king, but such their actions are utterly condemned and expressly forbidden by the law. Why therefore should you of the representative body sit still and suffer these lords thus to devour both us and our laws?
Be awakened, arise and consider their oppressions and encroachments and stop their lordships in their ambitious career. For they do not cease only here, but they soar higher and higher and now they are become arrogators to themselves of the natural sovereignty the represented have conveyed and issued to their proper representers.
They even challenge to themselves the title of the supremest court of judicature in the land — as was claimed by the Lord Hunsden when I was before them, which you may see more at large in a printed letter published under my name, entitled A defiance against all arbitrary usurpations  — which challenge of his I think I may be bold to assert was a most illegal, anti-parliamentary, audacious presumption, and might better be pleaded and challenged by the king singly than by all those lords in a distinction from the Commons. But it is more than may be granted to the king himself; for the parliament, and the whole kingdom whom it represents, is truly and properly the highest supreme power of all others — yea above the king himself.
And therefore much more above the Lords. For they can question, cancel, disannul and utterly revoke the king's own royal charters, writs, commissions, patents, etc. Yea the body representative have power to enlarge or retract the very prerogative of the king, as the Statute de prerog. And if the king's writs, charters, etc. And therefore these lords must needs be inferior to them.
Further, the legislative power is not in the king himself but only in the kingdom and body representative, who has power to make or to abrogate laws, statutes etc. For by law he has not a negative voice either in making or reversing, but by his own coronation oath he is sworn to 'grant, fulfil, and defend all rightful laws, which the commons of the realm shall choose, and to strengthen and maintain them after his power';  by which clause of the oath is evident that the Commons not the king or Lords have power to choose what laws themselves shall judge meetest,  and thereto of necessity the king must assent.
So that it cannot be denied but that the king is subordinate and inferior to the whole kingdom and body representative. Therefore if the king, much more must the lords veil their bonnets to the Commons and may not be esteemed the Upper House, or supreme court of judicature of the land.
So that seeing the sovereign power is not originally in the king, or personally terminated in him, then the king at most can be but chief officer or supreme executioner of the laws, under whom all other legal executioners, their several executions, functions and offices are subordinate; for indeed the representers in whom that power is inherent and from whence it takes its original can only make conveyance thereof to their representers, vicegerents or deputies, and cannot possibly further extend it.
For so they should go beyond themselves, which is impossible, for ultra posse non est esse: That which goes beyond the substance and shadow of a thing cannot possibly be the thing itself either substantially or virtually; for that which is beyond the representers is not representative, and so not the kingdom's or people's, either so much as in shadow or substance.
In September Overton proposed to turn spy, and so offered his services to Thurloe for the discovery of plots against the Lord Protector's government. If you do, it will be as little safe for yourselves and posterity as for us and our posterity. And the sovereign power not being inherent in him, it cannot be conveyed by or derived from him to any; for could he, he would have carried it away with him when he left the parliament. Thus sir, I have so far emboldened myself with you, hoping you will let grievances be uttered that if God see it good they may be redressed , and give losers leave to speak  without offence as I am forced to at this time, not only in the discharge of my duty to myself in particular but to yourselves and to our whole country in general for the present and for our several posterities for the future. Nothing but hanging, burning, branding, imprisoning, etc. In bonds for the just rights and freedoms of the commons of England, theirs and your faithful friend and servant, Richard Overton. Why therefore should you of the representative body sit still and suffer these lords thus to devour both us and our laws?
Therefore the sovereign power, extending no further than from the represented to the representers  — all this kind of sovereignty challenged by any whether of king, Lords or others is usurpation, illegitimate and illegal, and none of the kingdom's or people's. Neither are the people thereto obliged. Prynne denounced these tracts to parliament as the quintessence of scurrility and blasphemy demanding the punishment of the writer, whom he supposed to be Henry Robinson.
In Overton, who had been concerned in printing some of Lilburne's pamphlets, took up his case against the Lords, and published An Alarum to the House of Lords against their Insolent Usurpation of the common Liberties and Rights of this Nation, manifested in their Attempts against Lieutenant-colonel John Lilburne , An Alarum For this he was arrested by order of the house on 11 August and, refusing to acknowledge their jurisdiction, was committed to Newgate.
His wife Mary and his brother Thomas were also imprisoned for similar offences.
The New Model Army took up the cause of Overton and his fellow prisoners, and required that they should be either legally tried or released. He had a great share in promoting the petition of the London levellers on 11 September He was also one of those who presented to Fairfax on 28 December 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.
On 28 March he was arrested, with Lilburne and two other leaders of the Levellers, as one of the authors of England's new Chains Discovered. A refusal to acknowledge the authority of the Council of State or to answer their questions, caused his committal to the Tower.
On his own account he published on 2 July 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. The failure of the government to obtain a verdict against Lilburne involved the release of his associates, and on 8 November Overton's liberation was arranged.
In September Overton proposed to turn spy, and so offered his services to Thurloe for the discovery of plots against the Lord Protector's government. In the following spring he was implicated in the projected rising of the Levellers, and fled to Flanders in company with Lieutenant-colonel Sexby. Some months later he returned to England, supplied with Spanish money by Sexby, and charged to bring about an insurrection.