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British Spies and their Secret Invisible Ink

2 min read

The First World War opened so much experimentation for better weaponry, and surveliance. The spies of Britain were one of them, of course, as they experimented with all different variations of invisible inks.

In 1915, one of these spies divulged his discovery. He had learned to make invisible ink in the least expected way possible, and it was super handy. The secret sauce to the ink?

It’s semen.

The founder and head of MI6 at the time, and it’s not a pun we intended to make in this article, was named Captain Sir Mansfield Cumming. He reported the use of a weird method in creating invisible ink.

Sir Mansfield Cumming
Sir Mansfield Cumming

The only problem they had, of course, was over the course of time, if the semen wasn’t fresh and the letters would, well, smell like a cumbox.

One of the spies under the Brits was stationed in Copenhagen and he had amassed a good supply of semen in a bottle. When they arrived, everyone can smell the nastiness of dried copped up semen in the paper.

Spies using pigeons
Spies using pigeons

So Captain Cumming insisted that they use fresh semen as a requirement for every letter.

In the book “The Real James Bonds 1909-1939” written by Michael Smith, an excerpt about this wondrous invisible semen ink was mentioned in a letter by one of Cumming’s officers Frank Stagg:

Secret inks were our stock in trade and all were anxious to obtain some which came from a natural source of supply. I shall never forget [Captain Cumming’s] delight when the Chief Censor [Frank] Worthington came one day with the announcement that one of his staff had found out that semen would not respond to iodine vapour and told the man that he had had to remove the discoverer from the office immediately as his colleagues were making life intolerable by accusations of masturbation. The Old Man at once asked Coney Hatch [lunatic asylum] to send female equivalent for testing and the slogan went round the office — every man his own stylo. We thought we had solved the problem. Then our man in Copenhagen, Major [Richard] Holme, evidently stocked it in a bottle, for his letters stank to high heaven and we had to tell him that a fresh operation was necessary for each letter.

Well we can say that if enemies got wind of what the secret ingredient was, I’m pretty sure they will not see it coming.




Rudolph is a learner. He loves to read tons of stuff, from nutrition facts to novels. Currently, he helps people get unstuck with their homework as a Junior Market Specialist at Brainly. He also loves burgers.

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