Broadway meeting, 1648

In January 1648 Eyre attended the Broadway meeting where 80 officers of five regiments to discuss their men's grievances foremost of which is back pay. It is possible that the officers discussed plans for a mutiny and to pre-empt this, or for other reasons, in February Eyre's regiment was disband.^[2][5]

Henry Marten's Regiment in Berkshire, 1648

After the disbanding of his regiment, Eyre moved to Berkshire and aided Henry Marten (Eyre's farm was adjacent to Marten's estate), a member of the Berkshire county committee to raise a regiment of cavalry. The regiment was unauthorised by Parliament, but as the country was in the midst of the Second Civil War, Marten and Eyre ignored summons from Parliament and refused to appear in Westminster in person to explain themselves. The regiment was reported in the Mercurius Pragmaticus (a knowledgeable contemporary newspaper) said that the regiment claimed to be "for the people's freedom against all tyrants whatsoever" and were 1,500 strong, made up of serving Leveller troopers encouraged to leave (desert) their regiments for this unofficial one, and local yeomen farmers. They equipped themselves in various ways including they said requisitioning arms, ammunition and mounts from known delinquents such as Lord Craven. One of the victims of this unauthorised requisitioning was Sir Humphrey Foster. He named Eyre as one of the Offices involved in the requisitioning of this property, for which he had three men arrayed before the Assizes in Wiltshire. This move came to nothing when the men brandishing their swords refused to recognise the legitimacy of the arrayment.^[6]

Over the next few months the regiment was active in supporting the New Model Army and with his Presbetryan enemies purged by Pride the members of the Rump Parliament commissioned Marten's regiment into the New Model Army.^[6]

Burford mutiny, 1649

In May 1649 Eyre, who was now a civilian, took part in the Leveller-influenced Burford mutiny. He joined with the Salisbury mutineers and was captured at an inn in Burford on the night that Cromwell captured the Banbury mutineers at Burford Church. Eyre justified his actions in front of Fairfax and Cromwell by saying "if ... but ten men appeared for [the cause] , I would make eleven"^[7] Three days later Eyre was taken to Oxford and placed in its prison.^[2]

Imprisonment in Oxford and Warwick, and residency in Ireland

In July 1649, the Council of State was aware of unrest that would lead to the Oxford Mutiny; and not wishing to have a known mutineer in the area, ordered Eyre's transfer to Warwick Castle. While imprisoned there Eyre wrote to the Council of State recognising that he had made mistakes and had been misled; and requested that he might be given permission to join his family in Ireland. After spending about a year in Warwick, Eyre was released from prison on 1 August 1650. From there Eyre travelled to Ireland, and with the help of Henry Ireton, the Lord Deputy of Ireland, he gained possession of Shillelagh.^[2]

Nine years in prison

Eyre was briefly at liberty during the period of the restored Commonwealth of 1659. But was rearrested in May 1660 as a threat to the restored monarchy of Charles II. While being held in Dublin Castle he was accused of trying to foment a mutiny among the Irish foot guards, and while there was not enough evidence to try him for treason, the new regimen decided that he was too dangerous to release and was held in various prisons for the next nine years.^[2]

Appeals for recovery of his Irish estates

Eyre was released in December 1669, and with his daughter travelled to London to present his claim to the Shillelagh and Carnew Castle estates to parliament and King Charles. He published two appeals, the first was The Case of William Eyres, Esq. in which he accused the Earl of Strafford, C. Chambre, J. and Nathaniel Fiennes, J. Crew, Sir Philip Percival, the Countess of Carlisle, Leycester of Cheshire, J. Carpenter, H. Wentworth, Col. Jos. Temple, and others of illegally obtaining the estates comprising upwards of 60,000 acres (240 km²), while he was in prison. The second was titled A Particular Deduction of the Case of William Eyre, and described what Eyre considered his right to the Barony of Shelah and Castle of Carnow, in the County of Wicklow, that was in the possession of 2nd Earl of Strafford. The Earl of Strafford claimed that The Case of William Eyres, Esq. had libelled both himself and his father, and presented it as evidence to the House of Lords' Privileges Committee in May 1675. This is the last historical record of Eyre's life; there is no known record of what action if any the Privileges Committee took and of the rest of Eyre's life and death.^[2][9][10]