Thomas Myddelton, the son of Sir Thomas Myddelton, the owner of Chirk Castle, was born in 1586. Myddelton was elected to the House of Commons and represented Denbighshire.

On the outbreak of the Civil War, Myddelton, a committed Puritan, supported Parliament against Charles I. Chirk Castle was captured by royalist forces in January 1643. Given the rank of Major-General, Myddelton was put in charge of the parliamentary military campaign in North Wales.

Myddelton's main strategy was to cut off the king's military supplies that were arriving in North Wales from the continent. After capturing Wrexham in November 1643, his army headed for the ports of Wales' northern coast. Conwy, Bangor and Caernarvon were well defended and after 2,500 royalist troops arrived from Ireland, Myddelton was forced to withdraw.

Myddelton now turned his attention to mid Wales. In the summer of 1644 he captured Welshpool and Newtown and on 18th September the first major battle of the Civil War in Wales took place at Montgomery. The royalists suffered a heavy defeat and over 2,000 of their men were either killed, wounded or captured.

Myddelton's troops headed north and in October they were able to capture Powis Castle. However, despite strenuous efforts, Myddelton was unable to win back control of his own castle at Chirk. After failing to persuade Parliament to supply him with any more troops, Myddelton once again had to abandon his plan to try to win control of Wales' northern ports.

Myddelton was opposed to the trial and execution of Charles I. In 1659 he joined the Cheshire Rising proclaiming Charles II as king in Wrexham market place. As a result General John Lambert beseiged Chirk Castle.

On the Restoration Muddelton received £60,000 to recompense his losses. Sir Thomas Myddelton died in 1666.