High Quality Content by WIKIPEDIA articles! HMS Irresistible—the fourth British Royal Navy ship of the name—was a Formidable-class pre-dreadnought battleship. Commissioned in 1902, she initially served with the Mediterranean Fleet until April 1908, at which time she was transferred to the Channel Fleet. Now outclassed with the emergence of the dreadnought class of ships, she entered service with the Home Fleet in 1911 following a refit. In 1912, she was assigned to the 5th Battle Squadron.