HMS Alliance is a Royal Navy Aclass, Amphionclass or Acheronclass submarine, laid down towards the end of the Second World War and completed in 1947.

Over her 28year career, she held the world record for longest dive by a submarine, staying immersed for 30 days, in 1947, served during the Cold War, and was retired in 1973. The submarine is the only surviving example of the class, having been a memorial and museum ship since 1981.

In this video, submarine veteran Commodore Eric Thompson gives Dan Snow a tour of beautiful submarine, which is now preserved at the Royal Navy Submarine Museum in Gosport.

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