HMS Thetis cap band donated to Merseyside Maritime Museum in 2011. The donor’s uncle was involved in the salvage of the submarine. Accession number MMM.2011.13 On Sunday 1 June 2014 at 1pm a memorial will be unveiled at the River Walkway, Birkenhead. It will mark 75 years since the worst peacetime submarine accident in the history of the Royal Navy. On 1 June 1939 HMS Thetis sank in Liverpool Bay and 99 men perished. Thetis was built by Cammell Laird at Birkenhead and was launched on 29 June 1938. During sea trials she was carrying 103 men, twice as many was she was designed to carry. There were 53 crewmen, plus many engineers and observers from Cammell Laird, Vickers Armstrong and the Admiralty. On her very first dive she took on water and sank suddenly to the seabed. Through the night the crew worked doggedly to raise the vessel and were able to lighten the aft section enough to allow the stern to break the surface. The next morning four crew members, led by Captain Oram, escaped through a hatch using breathing apparatus. They were picked up by the HMS Brazen which had been diverted in response distress calls. Others attempted to escape in the same way but drowned when the hatch jammed. A cable was attached to Thetis, but this snapped and the submarine returned to the seabed. On Saturday 3 June the Admiralty announced there was no hope of any further survivors. The submarine’s unusually crowded conditions meant that the air would not have lasted long, causing those left on board to suffocate, poisoned by the carbon dioxide from their own breath. This tragedy prompted the introduction of the ‘Thetis Clip’. Still used by all British submarines to this day, it ensures the torpedo tube doors can only be opened a small amount in case the tubes are flooded - this was in part what had caused Thetis to sink. Thetis was raised and salvaged a few months later and saw service in the Second World War, having been recommissioned as HMS Thunderbolt. She was lost with all hands in 1943 and thus she became one of the few military vessels to have been lost twice with her crew. Derek Arnold, Chairman of the Liverpool Anchorage Club and son of Walter Arnold, one of the Thetis survivors, has been fundraising for a memorial to mark the 75th anniversary since last October. Appropriately, as many of those who died were workers from local shipyards, it has been very much a community effort. Derek told me that “donations came almost exclusively from the general public, mainly from the Merseyside area. This Sunday, during a short ceremony, the memorial will be unveiled at precisely 1pm. Anyone wishing to attend should make their way to the riverside walk, to the north of the Woodside Ferry Terminal. Due to the nature of the area there will not be seating available but free parking has been arranged with Peel Holdings on their premises at Woodside Business Park, CH41 1EL. Toilets and refreshments will be available at the ferry terminal. As the floral tributes are laid at Woodside, lifeboats from Moelfre, Llandudno and New Brighton will be casting theirs on the water at the site of Thetis' foundering."