The British domestic intelligence service has released espionage files dating from World Wars I and II, which it considers too old to be a security risk.
Spaniard behind the D-day landings
The success of the WWII allied Normandy landings was in part down to the audacity and imagination of Spanish double agent, Juan Pujol Garcia.

MI5: Interrogation, but 'no violence'
Spies caught on British soil were interrogated at Camp 020 - but MI5 reports say torture and violence were never used. Mata Hari gave MI5 the slip
MI5 has revealed that it had a file on the glamourous and infamous WW I spy Mata Hari, but it was unable to pin anything on her.

Airborne threat of Nazi pigeons
Nazi-trained pigeons were the target of British covert operations during WWII.