Supergun Submarine located 74 years after tragic loss
The British submarine, M1 which uniquely carried the firepower of a battleship was discovered 35 miles south-east of Plymouth at a depth of 81 metres by diver and submarine expert, Innes McCartney and boat skipper Grahame Knott.
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.
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.
Over the last 74 years, stories of the location of M1 have surfaced from time to time. None had ever been substantiated until 18th June 1999 when Innes McCartney's diving team returned with video evidence definitely confirming that M1 had at last been seen again.
For wreck hunters, McCartney and Knott, the location of M1 has been the culmination of over a year of detailed research. Archival records and local information from trawlers and other sources were used to narrow down a search area. M1 turned out to be the first target on their list to dive - successful research indeed.
In 1998, Innes McCartney located and dived the submarine Affray and has identified the final resting place of several U-boats, including the first operational submarine to be coated in rubber.
Of the wreck itself, McCartney says, "I knew it was M1 as soon as she appeared out of the darkness at 75 metres. She is upright and generally in good condition. However, she is festooned with 74 years worth of lost trawler nets. These were a major hazard to the diving team.
"M1 is a massive spectacle to behold, towering above the seabed by more than 5 metres. Her 12-inch gun has fallen away onto the sand. We suspect that it was struck during the collision with Vidar. The main damage to M1 is on the starboard side, forward of her huge bronze conning tower. This was a genuinely unforgettable dive".
Diving to such great depths requires the use of special helium/nitrogen/oxygen mixtures and is fraught with complexities. Few UK-based diving teams are able to employ this technology.
The position of M1 will remain a closely guarded secret in an attempt to prevent it being visited by souvenir hunters. She is a war grave, covered by the protection of the Military Remains Act, 1986. Mr McCartney's diving team did not interfere with the wreck in any way, returning after over 90 minutes of decompression with the only video footage of the wreck.