Intended as a shore bombardment vessel, M22s primary armament was a single 9.2 inch Mk VI gun removed from the HMS Gibraltar.[1] In addition to her 9.2 inch gun she also possessed one 12 pounder and one six pound anti-aircraft gun. Due to the shortage of Bolinder diesel engines that equipped her sisters, she was fitted with 2 shaft triple expansion steam engines that allowed a top speed of eleven knots. The monitor's crew consisted of sixty nine officers and men.
HMS M22 ordered in March, 1915, as part of the War Emergency Programme of ship construction. She was laid down at the Sir Raylton Dixon & Co. Ltd shipyard at Govan in March 1915, launched on 10 June 1915, and completed in August 1915.
M22 served within the Mediterranean from September 1915 to December 1918.
After service in the Black Sea from June to September 1919, M22 was towed home and converted to a minelayer in 1920. Renamed HMS Medea on 1 December 1925, she became a training ship in January 1937.