MI5's wartime secrets revealed: How a German spy was betrayed by a lemon

For the first time in its 110-year history, MI5 has opened up its secret archives.

Case files, photographs and original equipment used by MI5 agents are on public display.

The Secret Service Bureau, as it was originally known, was first set up in 1910 by a Royal Navy Commander and an Army Captain in an atmosphere of national paranoia about the infiltration of German spies.

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The first camera the agency bought was the Houghton Ensignette and cost just £3.10 from the Army & Navy store.

Less likely artefacts in the secret files exhibition at the National Archives in London include a mouldy lemon and a fake medal given to would-be German collaborators to lure them into revealing information.