A diary entry belonging to a senior member of the Secret Intelligence Service (MI6) has revealed that during the First World War it was discovered that the bodily fluid could act as an effective invisible ink.
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A member of staff close to "C", Frank Stagg, said that he would never forget his bosses' delight when the Deputy Chief Censor said one day that one of his staff had found out that "semen would not react to iodine vapour".
Stagg noted that "we thought we had solved a great problem".
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In addition, at least one agent had to be reminded to use only fresh supplies of the 'ink' when correspondents began noticing an unusual smell.
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Poster Comment:
So, any of you ladies want to see my "pen"...
It's got "invisible ink"...