'Spanner' was a British unrealised plan, suggested to the London Controlling Section at a time when strong British protests to neutral Spain about the activities of Axis agents in Algeciras opposite Gibraltar were bearing some fruit, to disguise the fact that it was 'Ultra' intelligence which had told the British about the Axis intelligence effort (July 1942).

Related to 'Assassin' (ii), 'Spanner' would have used a report that by a double agent that a Foreign Office official had let slip the supposed fact that a German agent had been bribed to betray both the nature and the extent of the Axis intelligence-gathering effort.