Key took command of the second-rate HMS "Sans Pareil" on the East Indies and China Station in January 1856 and went ashore with the naval brigade to take part in the Battle of Canton in December 1857 during the Second Opium War. He was appointed a member of the Royal Commission on the Defence of the United Kingdom in August 1859, became Captain of the steam reserve at Devonport in July 1860 and went on to be Captain of HMS "Excellent" and Superintendent of the Royal Navy College at Portsmouth in July 1863.