Vickers built the first six vessels of the class, the most famous and successful of which was HMS Midget Submarine XE3, commanded by Lieut. Ian Fraser, RNR, which attacked the Japanese heavy cruiser Takao on 31st July, 1945.
After being released from the towing submarine, XE3 spent more than 24 hours getting into a position to attack the Takao, which was moored in the Johore Strait, Singapore. After his first attempt failed, Fraser circled the target and put his boat under the great ship's hull. Despite being hampered by weed and barnacles and a leak in his diving equipment, the boat's diver, Leading Seaman James Magennis, swam along the cruiser's hull placing limpet mines. Exhausted he re-entered the submarine and XE3 pulled clear.
