HMS Unbeaten was a U-class submarine, the second of her class, built by Vickers Armstrong, Barrow-in-Furness. She was laid down on 22 November 1939 and was commissioned on 10 November 1940. So far she has been the only ship of the Royal Navy to bear the name Unbeaten.
She was 191 feet long and a little over 16 feet wide, displacing 630 tons, when fully loaded. She was propelled by two Paxman Ricardo diesel generators, each powering an 825hp electric motor and its own shaft. She had a crew of 27 and could reach speeds of up to 11 knots, whilst on the surface or 10 knots dived. She was armed with a single 3” gun, and up to 10 torpedoes, which could be fired through the four torpedo tubes in the fore ends.
She spent much of her career operating in the Mediterranean, where she sank the Italian sailing vessel V 51 / Alfa, the Vichy-French merchant PLM 20, the Italian submarine Guglielmotti and the German submarine U-374. She also claimed to have sunk two sailing vessels with gunfire on 15 July 1941 at Marsa Zuag roads, Libya, but Italian sources only confirmed damage to one fishing vessel.
Unbeaten also lightly damaged the Italian merchant Vettor Pisani on 16 March 1942. She also unsuccessfully attacked the Italian merchant Silvio Scaroni, the Italian troop transport Esperia and a large Italian troop transport, thought to be either Oceania or Neptunia.
After a refit in Chatham, and subsequent workup, HMS Unbeaten was attached to the 3rd Submarine Flotilla operating out of Scotland. Having sailed from Holy Loch on her last patrol on 23rd October 1942, Unbeaten completed Operation Bluestone, landing an intelligence agent in Spain near Bayona. She then completed her patrol in the Bay of Biscay and was returning to the United Kingdom when she went missing.
It was subsequently discovered that she was attacked and sunk in error in 11th November 1942 by a Royal Air Force Wellington of No. 172 Squadron, Coastal Command in the Bay of Biscay . She was lost with all hands in position 46º50'N, 06º51'W..
