For almost eight decades the artists’ model Louise Cansot, the subject of the novel winning France’s most prestigious literary prize this year, was one of Paris’s forgotten murder victims.

After her body was found near the Seine in September 1949, city police wrote off the young woman, immortalised as “the girl of 100 portraits”, as loose, libertine and – worse – an unmarried mother. They closed their investigation after just four months having made little effort to find her killer.

Lise Cansot by Charles Picart le Doux , 1949. Photograph: JLCOM

But long before the author Philippe Jaenada began researching his, Prix Goncourt-winning novel , L’ Inconnue du Quai de Javel (The Unknown Woman of the Quai de Javel) , another writer from the Breton village where Cansot was born had already spent decades researching her story.

Luc Corlouër might have felt aggrieved but in a rare show of literary solidarity, the two writers decided they would both publish books.…