On 11 September, 1943, a small team of men set out on what official records described as 'the most daring attack of the Second World War'. The secret mission pitted just a handful of British volunteers against an enemy several thousand strong. Crammed into four-man midget submarines, they battled for eleven days across treacherous Arctic seas. Their objective - an impregnable Norwegian fjord holding a foe one thousand four hundred times their size. The battleship Hitler called 'the Beast' - Tirpitz.