The other day I wrote about the importance of getting it right. 

You’re also free, I think, to get it wrong – even in a historical novel. Different writers have different thresholds, of course, but even the strictest acknowledge that when it comes to fiction it’s the story that really counts. Joan Aiken wrote a terrific series of historical novels for children, set in an 18^th century England where the House of Stuart still reigned: she got it wrong, but it felt absolutely right. What’s important is consistency.

In the Yashim stories I wouldn’t go that far. It is 1836, or 1840, and the sultan is the sultan. Venice is under Austrian occupation. You could buy champagne in Pera, on the shores of the Golden Horn. Gentile Bellini was, indeed, invited to Istanbul in 1479, where he painted a portrait of sultan Mehmed II. These, to me, are the Big Facts. There are lots more, and half the fun is weaving one’s imagination around them.

So one of my favourite characters is the validé, the sultan’s mother, whose astonishing story – from French ingénue to harem queen – is brilliantly recounted in Leslie Blanche’s The Wilder Shores of Love. She is Yashim’s friend in the palace. He appreciates her dry cynicism; she relishes his lurid tales from the City; and they share a fondness for Parisian novels.

But in truth, her presence in the harem is a matter of historical speculation, not certified fact, so no-one can say for sure whether she became the mother of Sultan Mahmud II. Either way, Mahmud’s mother was certainly dead by 1818: you can visit her tomb in Istanbul.

In The Bellini Card, set in 1840, she puts Yashim on the right track. She is very old; she is also very clever.

I wouldn’t lose her for the world.