Bendor’s — and Chanel’s — anti-­Semitism was vociferous and well documented; the pro-Nazi sensibilities of the Duke of Windsor and many in his circle have long been noted, too. All this, it appears, made the society of the British upper crust particularly appealing to Chanel. As Vaughan notes, after she was lured by a million-dollar fee to spend a few weeks in Hollywood in 1930 — Samuel Goldwyn, he writes, “did his best to keep Jews away from Chanel” — she found herself compelled to run straight back to England, so that she could wash away her brush with vulgarity in “a bath of nobility.”

It wasn’t much of a stretch, then, for Chanel, during wartime, to find herself the mistress of the German intelligence officer Baron Hans Günther von Dincklage, a charming character who had spied on the French fleet in the late 1920s, and who found himself pleasingly single in occupied Paris, having presciently divorced his half-Jewish German wife just before the passage of the Nuremberg Laws. It wasn’t any particular betrayal of her values, or morals or ideals either, for Chanel to find herself traveling to Madrid and Berlin to engage in cloak-and-dagger machinations with her country’s occupier.

The story of how Coco became Chanel has been told many times before over the past half-century, most recently (and, sad to say, much more engagingly) in last year’s “Coco Chanel: The Legend and the Life,” by the British fashion columnist Justine Picardie. The story of how Chanel metamorphosed from a mere “horizontal collaborator” — the mistress of a Nazi — into an actual German secret agent has been less well known, though earlier writers have reported that she had worked for the Germans. It’s here that Vaughan makes his freshest contribution, using a wealth of materials gleaned from wartime police files and intelligence archives, some of which were only recently declassified by French and German authorities, to flesh out precisely how and why she became an agent, and how she sought to profit from her German connections during the war.

Vaughan ably charts Chanel’s clever opportunism as she works, first, to free her nephew André Palasse from a German prisoner-of-war camp, and later seeks to use the Nazis’ Aryanization of property laws to wrest control of her perfume empire away from the Jewish Wertheimer brothers. Yet his account of her one real mission for the Germans — a 1943 covert operation code-named Modellhut (“model hat”) in which she was meant to use her contacts to get a message to Winston Churchill from the SS stating that a number of leading Nazis wanted to break with Adolf Hitler and negotiate a separate peace with England — emerges neither clearly nor logically from his highly detailed telling. Too many diplomatic documents are reproduced at too much length. Contradictions are not clearly sorted out. Vaughan seems to have felt as though his rich source materials could speak for themselves, but they don’t — and he doesn’t succeed in lending authority to the accounts of contemporary witnesses who were, undoubtedly, unreliable.

Despite her indisputable collaborationist activities, and after a brief period of uncertainty during which she was questioned by a French judge, Chanel eventually got off pretty much scot-free after the war, once again using her wiles to protect herself most expertly. She tipped off the poet and anti-Nazi partisan Pierre Reverdy, a longtime occasional lover, so that he could arrange the arrest of her wartime partner in collaboration, Baron Louis de Vaufreland Piscatory; she paid off the family of the former Nazi chief of SS intelligence Gen. Walter Schellenberg when she heard that he was preparing to publish his memoirs. (It was Schellenberg who had given her the “model hat” assignment.) Vaughan could have done better in providing the context to the seemingly incomprehensible ease of Chanel’s reintegration into French fashion and society, telling more, for example, of the widespread desire for forgetting and moving forward that held sway in Charles de Gaulle's postwar France.