When Geoffrey Tandy was summoned to Bletchley Park in 1939, he had no idea what to expect. A volunteer at the Royal Navy Reserves, Tandy wanted to serve Britain however he could as World War II threatened his country’s existence. But as a cryptogamist for the National History Museum, Tandy wasn’t quite sure where he fit in. Cryptogamists studied algae, a skill that wasn’t in high demand when it came to military strategizing.

Tandy was greeted by representatives for the Ministry of Defence, who seemed excited at the prospect of Tandy joining the top-secret efforts at Bletchley—too excited, really, about someone whose expertise was in seaweed.

At some point, it occurred to Tandy that the Ministry may have made a mistake. The exact details are lost to history, but it became clear that someone had mistaken his job of cryptogamist for a cryptogramist—a codebreaker, which is exactly what men like Alan Turing were doing at Bletchley. The mistake led to a moss specialist being deposited into one of the most intense covert operations of the war.

Generally useless to the group, Tandy did nothing for two years. Then something incredible happened.

In 1941, Allied forces torpedoed German U-boats and salvaged some important documents from the wreckages, including papers that instructed users of the German Enigma Machine how to unscramble messages. The problem: The papers were waterlogged, damaged, and in dire need of quick restoration before they could be put to use.

The Ministry needed someone who was an expert in drying out water-damaged, fragile materials. Someone who may have had training in preserving algae in such a manner. They needed someone like Tandy.

Using absorbent materials gathered from a museum, Tandy dried the pages and returned them to legibility. The Bletchley codebreakers were able to use the information to crack German communication, allowing Allied forces to get a glimpse of their strategy. The deciphering likely hastened the end of the war by two to four years, saving millions of lives in the process.

It’s not quite clear how Tandy’s fortunate misplacement occurred. Did a recruiter see a typographical error, with Tandy’s occupation getting the extra “R”? Or did someone simply misread it? Either way, the misunderstanding turned out to be quite fortuitous. Referencing the story in a 2012 speech, British politician William Hague said it demonstrated “just how useful wide expertise can be.”

[h/t: @floschecther]