As long as there have been valuable secrets there has been espionage. In the fifth century A.D., the Roman Emperor Justinian sent monks to China to steal secrets of the silk industry by concealing eggs of the silkworm moth in their walking sticks. In more recent times, professional spies have risked life and liberty in pursuit of crucial intelligence, usually on behalf of governments.
By the 20th century, the increasingly sophisticated level of spying techniques and technology, coupled with the high-stakes nature of modern espionage (especially that involving nuclear secrets), began making for some of history's most nail-biting spy escapades. In this feature eavesdrop on the chilling tales of 10 of the last century's most notorious spies.