Régina Diana: Seductress, Singer, Spy

Régina Diana was the nom-de-guerre of Marie Antoinette Avvico, the rebellious daughter of working-class French-Italian parents from a run-down part of Geneva. In December 1914, she appeared in the bustling port of Marseille to launch a triple career as a high profile French café-concert singer, a discreet and much in-demand prostitute, and a devastatingly successful German spy.

As part of a spy network spanning four countries, Régina Diana used her performing abilities and physical charms to entice soldiers at all levels - from privates to generals - into revealing their armies' secrets. Yet discovering the truth about Régina Diana herself involved a difficult and tantalising journey: getting past her disavowal by both France and Switzerland, overcoming the obfuscation of French military archivists, and digging into a three-line report about the death of a pretty Swiss chanteuse.

Even her execution was fittingly exceptional. To ensure she died as intended, the French high command doubled the size of her firing squad from the usual twelve rifles to twenty-five, and then consigned her to an unmarked grave.