This is Radio 4’s Saturday travel programme, presented by Sandi Toksvig.

Last week’s discussion was about Istanbul and Venice – which made a happy link to The Bellini Card, of course, although you’d miss the mention of the title if you sneezed!

http://www.bbc.co.uk/radio4/excessbaggage/

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. 

Nothing breaks the mood like a duff note – a glaring anachronism, a remark made in inappropriate slang, or the moment when your character’s eyes change mysteriously from blue to brown.

On the other hand, it’s important not to get too bogged down in verifying details when you’re writing. After all, it’s the story that counts, isn’t it?

Copy editing – which we’re doing now with The Bellini Card – is the proper time to address those niggles.

Is the name of the street spelled correctly? Do baby artichokes come into market before the asparagus?

Last week I even asked a fencing master round for tea, and we discussed the swordplay I’d written for the Contessa. It has been years since I fenced – sabre, not foil – but it turned out I’d got it almost right, except for calling octave optime; and he had a nice riff for me about a beat to the blade…

So The Bellini Card even has a fight co-ordinator!

On the question of slang,  I gave some minor characters in The Janissary Tree Cockney accents. I wanted to show that they were working men and women who’d grown up on the city streets: Istanbul, of course, not London. I think it was the right choice – I’m writing in English, after all. Decide for yourself, maybe.

I just checked with a friend whether women were able to work as calligraphers in the Ottoman Empire, transcribing the Koran.  

My answer arrived by email: a beautiful Hilya – a calligraphic portrayal of the Prophet – by an 18^th century woman calligrapher,  Esma Ibret.

Faber’s artwork for the UK edition has popped up on my screen! I like it enormously, just as I liked the covers of the first two Yashim novels, The Janissary Tree and The Snake Stone. They manage to look period and fun at the same time: bold colours, strong motifs, and a striking family resemblance, too. I get the feeling that the designers enjoyed themselves here, don’t you? 

A silhouette in a lighted window. A gondola. And a man in an extravagant turban, clutching a painting. It’s as if clues are being dropped even before you open the book.