Copper heater from the underground tomb. [Photo provided to China Daily]

And as a concubine, she had no right to be buried with the emperor.

For the last 10 years of her life, Zheng endured loneliness in a corner of the Forbidden City, in very much the same way as Empress Xiaojing, her invisible adversary once had. Her beloved son had long been dispatched to his own fiefdom thousands of kilometers away.

Zheng died aged 65 in 1630, 14 years before the Ming Dynasty fell.

Hu says: "If the word tragedy sums up the lives of Wanli's wives－either his loved one or his unloved ones－it is the word irony that sums up him, in life and in death."