Submarines intercepted the pirate-held SS Irene

The October 1927 encounter was an improvised use of submarines for counter-piracy rather than a planned special operation. L4 surfaced near the captured merchant ship and repeatedly ordered her to stop. When Irene continued, gunfire disabled the engine room and contributed to the vessel sinking. Fourteen people, apparently including both pirates and merchant sailors, died, while L4 and L5 helped save more than 230 passengers, crew, and pirates. Ten captured pirates were later executed. The account says officials tried to identify the civilian dead and compensate their families, and a later excessive-force damage suit was decided in the Royal Navy's favor. The case shows both the flexibility and the human risk of using whatever naval unit happened to be available.