Further to the on-going discussion of farts comes word that of all the hideous weapons devised during World War II — Little Boy, the Doodlebug, the bouncing bomb — the British secret service came up with the silliest.

Declassified letters in an American archive reveal that the Special Operations Executive (SOE), Winston Churchill’s cherished forerunner to MI6, set up a program to undermine German and Japanese officers in occupied countries by squirting them with stinking fluid.

Concealed in brass perfume sprayers or little gelatine grenades, the devices were designed to contaminate enemy officers with a “highly persistent smell suggestive of personal uncleanliness”.

In an exchange that could have been taken from a Monty Python sketch, a British military intelligence officer sent one of his US counterparts the complete plans for an olfactory weapon known as “S liquid”. The S was short for “stench”.

Based around skatole, a compound with an intense faecal reek produced by bacteria as they break down meat in the gut, it was intended to make Nazi officers the objects of mockery and contempt and sow alarm and confusion in their meetings.

On August 4, 1943, as the SOE was ramping up its campaign of sabotage in German-occupied France, Wing Commander TR Bird told Stanley Lovell of the American Office of Strategic Services (OSS), a predecessor to the CIA, how to make the obscene formula.

“Up to the present, our employment of evil-smelling substances has been mainly for the purpose of contaminating individuals’ clothing,” he wrote. “Since the air in any ordinary public meeting room is generally free from smell, almost any strange smell which cannot readily be accounted for would arouse suspicion which might easily culminate in fear or even panic.”

The officer appended sketches of an antecedent to the modern joke-shop stink bomb, which would release a gust of skatole when pierced with a pin, and a miniaturised cologne atomiser to be “carried about secreted in the hand or pocket”.

He also discussed the smell given off by the “stinking ant” found in South Africa, whose smell was thought to induce extreme nausea.

The papers were uncovered in the OSS archives near Washington by Mary Roach, a Californian science writer, during her research for Grunt, her book about science and the American military.