During the Second World War HMP Wandsworth played host to some of the UK’s most infamous spies.

But it also played a key in maintaining the secrecy of a double agent who transmitted false information via a wireless transmitter from inside the prison.

Between 1879 and 1939, 69 executions had been carried out at the prison’s gallows but that number was set to increase sharply with a new influx of inmates with alleged Nazi sympathies.

One prisoner received at that time was Arthur George Owens, the jail's first spy, who was held there as a double agent after feeding misinformation to the Germans.

As the owner of a battery company he often visited German shipyards before the war and had reported his observations to British agents.

At the start of the war, Owens was arrested because he was known to have also been in contact with the German intelligence service.

But Owens had second thoughts about working for Germany and told MI5 in September 1938 that he was to receive a radio transceiver.

The radio arrived via the left luggage office of Victoria Station early in 1939 and Owens turned this over to the authorities.

On August 11, 1939 he visited his German controller in Hamburg and on September 4, Owens returned to these shores with further German intelligence MI5 decided that he could act as a mole and detained him in Wandsworth Prison to sustain his cover.

On September 12, MI5 returned the transmitter to Owens at the prison where it was used by a warder to contact the Germans.

Owens received a reply inviting him to go to the Belgium, then neutral, and he was let out of jail to attend.

He was able to maintain his cover for some time and through Owens, MI5 was able to acquire clues to the existence of other spies and German strategies.

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