His father, Provo Wallis Sr., wanted a naval career for his son and, being knowledgeable about the rules for officers' entry into the navy, managed to get his son at the tender age of four, officially registered in 1795 as an able seaman on the 36-gun frigate Oiseau. In 1796 young Provo became a volunteer in the 40-gun frigate Prevoyante where he remained (on paper at least) for two years before returning command in the 64-gun Asia where he served until 1800 before being promoted as a midshipman into the 32-gun frigate Cleopatra.
Provo Wallis was then commissioned as a lieutenant on the 38-gun frigate, HMS Shannon in 1811. It was here that Provo Wallis gained most of his notoriety. The story is that the Shannon fought with the USS Chesapeake, commanded by Captain James Lawrence USN, near Boston on June 1, 1813, during the War of 1812. The relevant fact is that the Captain, Philip Bowes Vere Broke, was badly wounded during the action and the Shannon's first lieutenant was killed. Provo Wallis served as temporary captain of the British frigate for a period of exactly six days as she made her way back to Halifax, Nova Scotia, with the Chesapeake flying the Blue Ensign above the Stars and Stripes.