Secret MI5 file sheds light on wartime spies in Gibraltar

The crucial role of intercepted German signals intelligence in wartime Gibraltar is laid bare in a secret MI5 report released to The National Archives today.

The newly-declassified 47-page report was written at the end of the war by Herbert Hart, the head of MI5’s B1B section, whose role was to analyse decrypted communications picked up from the Abwehr, German military intelligence.

The highly-classified material, obtained by codebreakers at Bletchley Park, was crucial to identifying and capturing suspected German agents in Britain and around the world.

It also played a key role in Gibraltar where the intercepted material, known by the acronym ISOS, provided “the first authoritative information about German espionage in the fortress of Gibraltar and the Campo area”.

But while Hart sets out how the secret German intelligence was used to help detect agents in Gibraltar, he also reveals how organisational structures in Britain’s intelligence community meant valuable information often did not make it to the Defence Security Officer (DSO) on the Rock, whose job it was to catch enemy spies.

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