His last act on behalf of the English crown came in July 1666 when, having learned of the recent French seizure of Saint Kitts, he formed a relief force of two Royal Navy frigates, twelve other large vessels (including commandeered merchant ships), a fire ship, and a ketch, bearing over 1,000 men. He planned to proceed north to Nevis, Montserrat, and Antigua to gather further reinforcements before descending on the French. Leaving Barbados on 28 July, his force prowled off Martinique and then Guadeloupe, where he sent a frigate to assault the harbor and capture two merchant vessels on 4 August. This success could not be exploited however as that night most of his force was destroyed by a strong hurricane, including the flagship "Hope", from which Willoughby did not emerge.