H.M.S. Unicorn joined the Royal Navy in 1789. She was built as a frigate carrying 32 guns capable of firing 12 and 18 pound shot. She was larger and faster than other British frigates of her rate and was designed by the noted naval architect, F.H. Chapman, following his pioneering studies of hydrodynamics. She was capable of sailing in heavy wind without excessive pitching or rolling.
Frigates evolved as a new kind of fighting ship during the latter half of the eighteenth century. They were long, low, sleek sailing ships, capable of maneuvering and of sailing close to the wind. Unlike the slow, heavy ships of the line, whose very reason for existing was to engage, like contending herds of elephants, in huge thundering fleet actions, the agile frigates were free- spirited ships capable of a wide range of missions. Darting about courageously, the frigate was the cruiser and destroyer of its day, and its captain was generally given the widest latitude for engaging in independent action. They were unexcelled at harassing and capturing enemy shipping. They performed essential courier services. They enforced blockades. They slashed through the lines to relieve beleaguered ports. In major actions, they were the eyes of the fleet. They rescued big ships of the line damaged in action. In the Battle of the Nile, Nelson proclaimed "were I to die at this moment, want of frigates would be engraved upon my heart".
The Unicorn participated heroically in most of Lord Nelson's victories against the Spanish and French fleets at the turn of the century. She formed part of the scouting line at the Battle of the Nile and she served valiantly at the Battle of Trafalgar, performing two major rescues while under fire. During the British-American war of 1812, she performed blockade duty in Long Island Sound and at the mouth of the Chesapeake Bay. She was finally overtaken by old age and sank during a storm in 1823.