In November 1756 Cornwallis was one of three colonels who were ordered to proceed to Gibraltar and from there embark for Menorca, which was then under siege from the French. Admiral John Byng called a council of war, which involved Cornwallis, and advised the return of the fleet to Gibraltar leaving the garrison at Menorca to its fate. Byng, Cornwallis and the other officers were arrested when they returned to England. A large, unruly mob attacked the officers as they left their ships in Portsmouth and later burned effigies of Cornwallis and the other officers.