For the best part of three years now, I have been living with an impossible woman. While it’s a love affair of sorts – why else would I put up with it – her intransigence, snobbery and occasional downright bolshiness have, at times, been a trial. But in return she offers an incandescent appetite for life, a passion for art, independence in the face of male power and the resilience to stand up to whatever fate throws at her.

Her name is Isabella d’Este, and if I tell you that she’s been dead for close on five hundred years, you’ll probably understand my predicament as a novelist.

I got to know her (aided by the work of some excellent Renaissance scholars) in the reading room of the state archive of Mantua, once a thriving state in the north of Italy, where from 1490 to 1539 she lived as wife and then widow to Marquis Francesco Gonzaga II. She was a pioneering woman patron; her collection was a stunning mix of contemporary works (by Leonardo, Mantegna and Perugino, to name but a few), Roman and Greek statuary, antique medallions, first editions of books, instruments and anything else that took her fancy, all of which have long since been scattered to the winds. But from the novelist’s perspective her greatest achievement is intact: her correspondence, some thirty-three thousand letters and replies, now crammed into battered files and boxes inside the cavernous space of a deconsecrated church in Mantua.

The Mantuan state archive came into existence (as in other former city-states) with Italy’s reunification in the late 19th century, when the country was in the business of creating a national history. Reports of the time tell of how carts and wagons filled with boxes and chests were