"The German high command gave orders to the SS to annihilate the entire population because the Americans were coming closer, " Avital said.

WSJ: Holocaust survivor, liberator meet for first time

Mr Roberts, of Hampshire, was among four founder members of the Testery section tasked with breaking the German High Command's Tunny code.

BBC: Raymond 'Jerry' Roberts

The target messages, enciphered with a Lorenz S42 machine as used by the German high command, were transmitted by a team of radio enthusiasts in Paderborn, Germany.

BBC: Colossus in operation during wartime, PA