Ironically, she would have reveled herself: Author Barbara Pym, who pierced the social restrictions of 20th century Britain, served as a censor during World War II.

But research shows that she may still be working for MI5, not just taking a closer look at private letters that must help hone her talents.

Claire Smith's new work this week proposes that PYM's time as a "censor" for the government and the navy is more than just a story about poachers of future satirists.

"In one of her novels, she said it was really boring to be an inspector. But when I started to look at her, I found a lot of strange things."

She believes that PYM's keen eye for details is used to encode messages and secret writing, and, in other normal terms, becomes one of a group of female inspectors receiving special training.

Smith, who worked in foreign and Commonwealth offices for 27 years, was the only female diplomat to negotiate with the Taliban, said: "They were looking for micro dots, secret writing, secret writing, information hidden in ordinary letters. Since Pym is a writer, she would have noticed the strange way of building sentences. She was very valuable."

Dame Jilly Cooper describes Pym as the author, who “brings me happiness and tender laughter than any other writer.” But before she got the spotlight for works like excellent women and a cup of blessing, Pym was looking for publishing in the pre-war era.

Instead, she became an examiner in 1941, ostensibly accused of examining private letters between Irish families in England and Ireland.

"I think it's weird that Oxford graduates who speak German and have written should actually only look at letters between Irish families," Smith said.

Pym traveled to Germany several times in the 1930s and even established a relationship with a young Nazi official.

This study is World War II: The British Naval Censorship of Ignored Intelligence Functions, published with the support of the Barbara PYM Association. It matches the house commemorating Pym's Pimlico in London and has a blue plaque with British heritage.

In the Bodlia Library at Oxford University, Smith found in PYM's notebook and diary that she wrote articles about learning code while reviewing, and even how to submit MI5.

"If you're just reading everybody's letter to knock out taboo parts, why learn the code?" Smith said.

PYM's time as a postal examiner for the Women's Royal Naval Services (nicknamed Wrens) also grasps the key clues to hide the past.

She was promoted quickly and became a Navy inspector in Southampton as Admiralty prepares for D-Day, and then saw the rest of the war in Naples.

It was during her time on the South Coast that the biggest strange event happened, Smith said. "In World War II, the MI5 used the PO Box 500 as its address, and in communications they were often called the 'Box 500'. This is completely different from the box number used by naval personnel.

“But, on the back of a letter outside of the UK, Pym (written by her own hand) wrote her abbreviation (Naval Land Base) HMS Mastodon and Box 500.”

The blue plaque will be placed at 108 Cambridge Street, Pimlico. British historian Susan Skedd called it a "real honor to honor Barbara Pym who found such rich materials".

"Barbara Pym is a genius writer - brave, kind, smart, smart, smart, funny and endlessly rereading," said Devon Allison, chairman of Barbara Pym Society.

Historian Lucy Worsley said: "This blue patch celebrates her great contribution to British literature and her ability to find extraordinary in ordinary terms."

The last part of the puzzle Smith stumbled upon is that after Pym's death, her literary executor "does his best to say a work, a comic spy thriller is very secretive and has not succeeded because Pym doesn't know any spies".

Smith said: "I thought: Why do you say that?"