Diana's first action came quickly. On August 8, 1807, she intercepted Topaze, an American pirate schooner, near Macao. Kempthorne led the boarding from a jolly boat and was knocked overboard, badly wounded in the head and back by boarding pikes. Most officers would have retired to lick their wounds. Kempthorne climbed back in when a cutter came alongside and resumed the attack. Twenty-nine of Topaze's crew were killed or wounded; Diana lost three men wounded. The pirate vessel was condemned as a prize. A year later, on August 6, 1808, Diana took the Dutch national brig Vlieg, which lay anchored under the guns of a fort at Serookie in Java. Vlieg carried six long 6-pounder guns and a cargo of brass cannon destined for Surabaya. Neither the fort nor the guns deterred Kempthorne.

Toward the end of 1808, Rear-Admiral Drury wanted to pressure the Chinese government into meeting British demands. He assembled a miniature squadron -- Diana, a prize brig, and the East India Company vessel Discovery -- and sent Kempthorne up the Pearl River to Canton. The tiny force blockaded one of the world's great trading cities until Drury called off the demonstration. From there, Diana and Discovery sailed to Manila in January 1809 to retrieve Captain William Pakenham and the crew of a frigate that had wrecked in the Philippines the previous October. The Spanish released the British sailors on parole. It was on the return voyage that Diana's luck was tested hardest.

Near Pulo Aor, Diana and Discovery encountered two French frigates, including the Canonniere and a captured Royal Navy post ship. The French gave chase, driving the two British vessels toward the Straits of Singapore. Diana was hopelessly outgunned. Kempthorne made the ruthless calculation: he ordered every gun thrown overboard to lighten the ship, then sailed past Point Romania near Pedra Branca at maximum speed, slipping through a gap the heavier frigates could not follow. Diana escaped. Discovery, carrying Captain Pakenham and his officers, did not. The French captured her and took their prisoners to Batavia. Kempthorne had saved his ship by sacrificing her teeth -- a decision that would leave Diana unarmed when she next needed to fight.

By September 1809, Diana had been re-armed and was prowling the waters off Celebes. On September 10, she sailed into Amurang Bay and spotted the Dutch 14-gun brig Zephyr anchored beneath a fort. Kempthorne sent boats in under cover of darkness, only to find the anchorage empty -- Zephyr had slipped away. Guessing she had run to Manado some 40 miles north, Kempthorne gave chase. He sighted her the following evening, but Zephyr reached the protection of Manado's fort guns before Diana could close. When a gale blew up, Captain-Lieutenant Gillet Vander-Veld sailed Zephyr out, hoping to fight in open water. Diana engaged her for 70 minutes. Zephyr struck her colors with five dead and eight wounded out of a crew of 45. Diana suffered no casualties. A few well-aimed shots dispersed five gunboats rowing out to help the Dutch vessel. Diana took Zephyr in tow and departed. In 1847, the Admiralty awarded the Naval General Service Medal to surviving veterans of the action.

Diana's later career was less glamorous. She grounded on reefs south of Great Natuna Island -- reefs Kempthorne named the Diana Reefs, a modest form of cartographic immortality. In May 1810, she was surveyed and laid up at Rodrigues in the Indian Ocean. A mistaken entry in Steel's List reported her wrecked, and this clerical error delayed the promotion Kempthorne had been recommended for after capturing Zephyr. He did not receive his commission as Commander until April 1811. For a ship the Navy barely knew what to call, Diana left an outsized mark: three armed vessels captured, a city blockaded, a legendary escape, and a 70-minute single-ship action that earned medals four decades later.