Castle Cornet, situated on the island of Guernsey, was the last bastion of support for King Charles II during the Third English Civil War. Following Charles's defeat at the Battle of Worcester in September of 1651, he fled to Scotland, leaving his loyalists in Guernsey to fend for themselves. The Parliamentary forces, seeking to eliminate all Royalist strongholds, laid siege to the castle, which had been fortified and held by Royalists loyal to the King. Sir Henry Seymour, who commanded the garrison, managed to hold out against the siege for months, but eventually, the provisions dwindled and morale slipped among his troops as they faced relentless shelling and bombardment from the besieging forces. Despite limited resources, the Royalists' resolve remained steadfast until the very end.As the siege dragged on, the political climate in England shifted more in favor of the Parliamentarians, emboldening their efforts to quash any remaining Royalist opposition. On December 15, 1651, Sir Henry Seymour made the difficult decision to surrender Castle Cornet. The Royalists within the fortress were allowed to leave in peace, marking an important moment in the transition of power. The surrender effectively ended organized Royalist resistance in the Channel Islands and led to the establishment of a Parliamentarian governance structure, solidifying their control over the region. This moment also heightened tensions between the loyalists and the new rulers, laying the groundwork for future conflicts and political struggles in Britain.