MI6 agents used ‘bodily fluids’ as invisible ink

SERVING officers experimented with using semen as an invisible ink to write top-secret letters during the World War I, according to Keith Jeffery’s book.

A senior officer found that the bodily fluid could act as an effective invisible ink which did not react to the main methods of detection. Better still, it had the advantage of being readily available.

But the plan fell apart with problems when correspondents failed to use fresh urine and an unusual smell was detected.

Other anecdotes include miniature cameras disguised as matchboxes, shoe brushes with secret compartments, and — as if straight from Q’s laboratory in the Bond films — a pen which fired tear gas pellets.

Among the controversial files he studied was an account of MI6 agents sabotaging ships due to carry Jewish refugees to the then British Mandate of Palestine, immediately following the end of World War II. MI6 aimed to blow up ships in port preparing to take Jewish refugees to Palestine. At the time, Britain was still ruling Palestine and politicians ordered the service to stop the flow of refugees.