British M-class submarine

HMS Submarine M1 was developed toward the end of the First World War. Unique in the history of submarine design, she and her sisters M2 and M3 were fitted with 12 inch guns from a scrapped battleship. This gave the M-Class the ability to sneak-up on shore installations and surface vessels, rise to the surface and deliver a formidable blow from very short range. No merchant vessel was expected to survive a hit from M1.
M1 was completed before the war ended, but not employed in combat because the Royal Navy feared that Germany could copy the design. The U-boat war against British commerce might have taken a grave turn for the worse if such deadly weapons had been employed against Britain s merchant marine.
After the war, the M-Class submarines were used experimentally in developing a range of new submarine technologies. M3 was converted into a minelayer and later scrapped in the 1930s. M2 was converted into the world's first submarine aircraft carrier. She carried a miniature stainless steel-framed seaplane. M2 was also lost in tragic circumstances in January 1932.
M1 disappeared with her entire crew of 69 while submerged on exercise on 12th November 1925. Her loss remained unexplained until the collier Vidar entered Stockholm on the 19th. She reported being in collision with a submerged object off the Devon coast. Investigation of her damaged bows showed traces of a rare paint which had been used on M1. Navy divers and survey vessels searched for M1 for a month before abandoning hope of locating her.
Her wreck was discovered by a diving team led by Innes McCartney in 1999 at a depth of 73 m. Later that year, the wreck was visited again by Richard Larn and a BBC TV documentary crew, and the resulting film was broadcast in March 2000. The wreck is designated as a protected place under the Protection of Military Remains Act 1986

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