Morgan probably remained at liberty throughout his time in London, and the political mood changed in his favour. Arlington asked him to write a memorandum for the King on how to improve Jamaica's defences. Although there was no court case – Morgan was never charged with an offence – he gave informal evidence to the Lords of Trade and Plantations and proved he had no knowledge of the Treaty of Madrid prior to his attack on Panama. Unhappy with Lynch's conduct in Jamaica, the King and his advisers decided in January 1674 to replace him with John Vaughan, 3rd Earl of Carbery. Morgan would act as his deputy. Charles appointed Morgan a Knight Bachelor in November 1674, and two months later, Morgan and Carbery left for Jamaica. They were accompanied by Modyford, released from the Tower of London without charge and made the Chief Justice of Jamaica. They travelled on board the "Jamaica Merchant", which held cannon and shot meant to boost Port Royal's defences. The ship foundered on the rocks of Île-à-Vache and Morgan and the crew were temporarily stranded on the island until picked up by a passing merchant ship.