A nazi spy came within days of uncovering one of the Allies' most important missions and possibly changing the direction of the Second World War.
The story of a Portuguese wireless operator and the dramatic decision to pluck him from his vessel on the high seas to prevent him from betraying the position of a huge convoy bound for North Africa is revealed for the first time in a declassified MI5 file released by the National Archives.
Gastao de Freitas Ferraz was being paid by German intelligence to send coded messages about convoys to U-boat commanders and was on the tail of the Allied warships.
The convoy included the USS Augusta, an American light cruiser that was carrying no less a person than General George S.Patton.
General Patton was at that time in command of Operation Torch, the planned invasion of French North Africa, which was aimed at destroying the Axis forces fighting the British there and improving naval control of the Mediterranean.