So, when Conger visited Cixi with fellow survivors of the siege, and on subsequent occasions was photographed holding her hand - the only known image of Cixi touching a foreigner - she was, as might be expected, misunderstood, in her own country, in diplomatic circles, and even by her husband.

"In the foreign press of the day, Sarah Conger was blamed for taking a hand 'washed in the blood of Christians'," says Hayter-Menzies, "while Cixi was blamed by the conservative Chinese for befriending a Christian foreigner".

The tie remained strong and steadfast until Cixi's death in 1908, well after Conger went back to the United States and curated an exposition on China at St. Louis in 1904, where Cixi's portrait by Katharine Carl held pride of place.

"Sarah strongly believed the integrity of China's culture and political structure should be preserved from foreign meddling, including that of Christian missionaries," says Hayter-Menzies.

"She also believed the West nursed a skewed image of the East in general and Cixi in particular, and that if people outside China could see the Empress Dowager as she knew her, the caricatures would fade and the truth of both Cixi and China would emerge."

The "truth" about Cixi seems bizarre and fantastical in Decadence Mandchoue. The idea of a young English baronet, polyglot and homosexual - who slept with illustrious writers and artists of the 1890s, including Oscar Wilde and Aubrey Beardsley - getting involved with a 69-year-old empress is way too twisted for people with regular tastes.

"To assume sexual encounters are not true because it's too fantastic is dangerous," says Sandhaus. "Backhouse is a Victorian aristocrat who left high society to come and live in Beijing for 50 years. He is weird. And I would think living with absolute power within the precincts of the Forbidden City could produce weird behavior in the bedroom."

There is more explosive stuff. Backhouse suggests Emperor Guangxu was, in fact, poisoned by Cixi. Sandhaus draws attention to forensic tests conducted in 2008 that have revealed heavy traces of arsenic in Guangxu's remains, insinuating Backhouse might not have been too far off the mark. "But it would have been impossible to say it then."

Conger, too, wrote a book on her impressions of Cixi. In Letters from China: With Particular Reference to the Empress Dowager and the Women of China (1909), she wrote about the disarming warmth Cixi showed toward her, about her insatiable curiosity of the world outside China, and also, rather presciently, about "the wonderful awakening" that made the Chinese "reach for something outside of their great nation and their long-time customs and ideas". She saw Cixi as a living embodiment of that reaching out and trying to find China its rightful place in the world.

"She had a powerful curiosity about the way the world worked," Hayter-Menzies says. "She was genuinely interested in the future and China's role in it, especially vis--vis the United States, which she often declared was her favorite foreign country and the one she most wanted to visit."

Cixi's hunger for knowledge and experience is an overriding element in both Decadence Mandchoue and The Empress and Mrs. Conger. Her experiments of the purely physical kind in the former are punctuated by an insatiable curiosity about what Queen Victoria or, a Russian tsarina might do in her situation.

She comes through as a champion of universal sisterhood and women's education in The Empress and Mrs. Conger.

"It was education which had opened doors to Cixi at the imperial court, alongside Emperor Xianfeng and later as regent and administrator," Hayter-Menzies says. "Conger found in Cixi a willingness and interest in furthering education for Chinese girls." After Sarah returned to the United States, her women friends in China sent regular reports of their progress, including news of the school set up by Cixi's adopted daughter, he adds.

Hayter-Menzies does not set much store by the tales of the empress' juicy hook-ups, with Backhouse, or, for that matter, others, like Cixi's favorite eunuch Li Lianying, or grand secretary Junglu, a childhood friend.