HMS Irresistible—the fourth British Royal Navy ship of the name—was a Formidable-class pre-dreadnought battleship. The Formidable-class ships were developments of earlier British battleships, featuring the same battery of four 12-inch (305 mm) guns—albeit more powerful 40-calibre versions—and top speed of 19 knots (35 km/h; 22 mph) of the preceding Canopus class, while adopting heavier armour protection. The ship was laid down in April 1898, was launched in December that year, and was completed in October 1901. Commissioned in 1902, she initially served with the Mediterranean Fleet until April 1908, when 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,