How MI5 won secret war against Nazi supporters

Antifascist protesters target BUF leader Oswald Mosley in 1943 Picture: Getty

Files released by the National Archives show that the motley array of traitors and “fifth columnists” active in Britain during the Second World War was totally penetrated by the security service.

MI5 even drew up plans to issue them with badges to be worn in the event of an invasion – supposedly to identify them as friends to the Germans, but in fact to enable them to be swiftly rounded up by the police.

The service also acquired replica Iron Crosses to reward members of the network for their loyalty, while adding further proof that they were actually working for the Germans.

At the centre of the operation was a MI5 agent, known by the alias “Jack King”, who was said to have a “genius” for such work.

By the end of the war, MI5 estimated that he was able to monitor and control the activities of hundreds of would-be traitors who were in fact acting as “unconscious agents” of the British.

King – who is also referred to as SR in the files – initially began by attempting to penetrate Siemens Schuckert (GB) Ltd, the British arm of the German industrial giant which was suspected of conducting espionage for the Nazis.

But the plan changed when in 1942, during the course of his inquiries, he met a “crafty and dangerous woman” called Marita Perigoe.

Said to be of mixed Swedish and German origin, she was married to a member of Oswald Mosley’s British Union of Fascists (BUF) who had been interned in Brixton Prison.

She, however, had no time for the BUF, regarding them as “insufficiently extreme”.

“She was found to be so violently anti-British and so anxious to do anything in her power to help the enemy that it was felt that special attention should be paid to her,” MI5 reported.

In order to penetrate her network of fifth columnists, King convinced her that he was a representative of the Gestapo looking for people “a hundred per cent loyal to the Fatherland” who could be relied on to help in the event of an invasion.

Initially, he sought to exploit the group’s taste for the cloak-and-dagger aspect of espionage work, offering to supply them with invisible ink for secret communications.

“The organisation has certain somewhat melodramatic ideas about secret service work and to gratify these a suitable meeting place in the basement of an antique shop has been found,” MI5 reported in 1942.

“Arrangements have been made to record any conversations that take place there.”

As King’s network expanded, MI5 looked at new ways to subvert its activities.

“It is proposed at a later stage to provide all members of the organisation with badges, which will probably take the form of some innocuous object like the Union Jack, which they will be instructed to hide until orders are given from headquarters,” one report stated.

“From then onwards they will wear them. The object of this plan is to enable the police easily to identify members of this fifth column organisation in time of emergency.”

By the end of the war, Perigoe was one of six agents working directly for King. MI5 estimated the numbers of their contacts who had been the subject of his “SR” intelligence reports ran “certainly to scores and probably to hundreds”.