As commanding officer of the fifth-rate HMS Madagascar, Wallis earned the thanks of the people of Veracruz in Mexico when he protected them from French bombardment during the Pastry War.

He was the son of Provo Featherstone Wallis, a clerk at the Royal Naval Dockyard, Halifax, Nova Scotia, by his wife Elizabeth Lawlor.

Knowing the rules for an officer's entry into the navy, his father managed to get him officially registered in May 1795, at the age of four, as an able seaman on the 36-gun frigate HMS Oiseau, under Captain Robert Murray.

[2] In an action on 16 February 1805, HMS Cleopatra was captured by the French frigate Ville de Milan and the ship's company taken prisoner of war.

[5] Wallis served as the temporary captain of the British frigate for a period of exactly six days as she made her way back to Halifax, Nova Scotia, with Chesapeake flying the Blue Ensign above the Stars and Stripes, for which action he was promoted to commander on 9 July 1813.

[5] Appointed as commodore (but remaining a post captain in substantive rank) he went on to be Senior Naval Officer, Gibraltar, with his broad pennant of the third-rate HMS Warspite, in October 1843.

[5] Promoted to rear-admiral on 27 August 1851,[6][4] Wallis became Commander-in-Chief, South East Coast of America Station, with his flag in the third-rate HMS Cumberland, in May 1857 but only held the command until September 1857.