Here is almost nine minutes of British Pathe newsreel footage of the Royal Navy's "submarine cruiser" HMS X.1 at sea, circa 1925.covert_shores said:HMS X-1 (not an X-Craft!!!) built in 1920s. The guns were only 5.2" but mounted in twin enclosed turrets. For a time she was the largest submarine in the world. Very cool boat.
The British K-Class is also worth a look in, definitely cruiser submarines although the guns are less big.
YouTube: British Pathé - "The Undersea Battleship Arrives (1925)" - FILM ID:372.09