"About five years ago, I saw a newspaper report that said, during the Gulf War, Saddam Hussein had the habit of dropping in unannounced on ordinary families in Iraq. That struck me at the time as a wonderful idea for a play. It fomented in my head for about three years until, last year - January, February and March - I had a window where I could just write, not for television, not for publishers, not for Hollywood producers, but for me."
So, a new book, a new play and a new TV series all in full swing - how bad a week could it have been? Well, there is the little matter of what might be called the Idris Elba affair.
In a recent interview for the Mail on Sunday Horowitz was asked about who might play the spy after Daniel Craig. Elba would be "a bit too rough" and "a bit too street" he said. It was this last phrase that caused the storm. It was taken by many as a euphemism for black, even though in the same interview Horowitz also said "it's not a colour issue", but a question of which actor can do "suave". He also said that Hustle star Adrian Lester, who is also black, might do it better. Yet still the complaints came piling in, causing Horowitz to release a fulsome apology.
''It has been a very unfortunate experience," he says, now choosing his words with the greatest of care. "I inadvertently used language that was apparently clumsy. And once again, as I said in my statement, to cause such offence upset me very much. It really did." But was the criticism fair? Is ''street'' even a racist term?
"When I used the word 'street' I was comparing one black actor with another black actor. I used the word ill-advisedly…" he says, staying tenaciously on message.
The thing - or one thing - about Horowitz is that, as Trigger Mortis shows, he is a master plotter. It's all a question of taste, of course, but you could say that, in Horowitz's hands, the character of Bond serves plot, while in the Sam Mendes-directed films, plot takes second place to character. And, although Horowitz may regret pointing out that the final showdown in Skyfall, in which an unarmed Bond takes M to a secluded house is not the most logical way of protecting his boss, Horowitz is surely right. It must be difficult to see perceived flaws and keep shtum. That said, Casino Royale was, says Horowitz, one of his all-time favourite Bond films. And that was produced by the "same team" as did Skyfall and the forthcoming Spectre: Craig and producer Barbara Broccoli. Yes, but it wasn't directed by Mendes.
"I have learned from the last two weeks, particularly when you're dealing with a brand as world famous as James Bond, you just have to be more circumspect." He seems bruised by the affair.
"You are talking to me after a very trying week," he stresses. "All my good intentions, and the work of a lifetime have been thrown into question and, worse than that, have been traduced, by the suggestion that I have attitudes that I don't have." Then he backtracks. "Maybe not traduced," he corrects.
I say it all seems especially unfair considering that he has just written a Bond book that manages to avoid offending modern audiences while acknowledging the casual bigotry of Fleming's original character. Goldfinger, for instance, was referred to as Jewish in a derogatory way, explains Horowitz. And Bond also uses casually homophobic terms such as "pansy".
You need to have a good politically correct radar to tread through that minefield. It is a sensitivity that might come as a surprise given that Horowitz's bearing and public school accent suggests that he is an establishment figure through and through. His father, who died of cancer when Horowitz was 22, has been described as a secret fixer for Harold Wilson. Then there was the ''horrendously unpleasant'' prep school and the family house with servants, all of which must have given him early insights into the life of the ruling class.
"I've never really been an establishment figure," he maintains. "First of all, I'm Jewish. I've never thought of myself as mainstream because my work is too varied.
"I suppose people would say I'm privately educated. But does that make me an establishment figure? No, I've always thought of myself as an outsider. It was a childhood of great privilege. I hate hearing myself complain about it. There are children given a great deal less than I was given. But it was also very odd being trapped in this rather bizarre family in this large house with servants." As for religion, he was turned off by his experience of it.
"Unfortunately, I was sent to a Sunday school as a chubby and not very bright 11-year-old. I was badly teased and I had a rather rough time of it, and couldn't quite come to grips with Hebrew. Or any of it, really. It didn't help that my father who eventually had an Orthodox funeral, himself had a very odd relationship with his religion. We didn't observe anything as far as I could gather. My brother was barmitzvahed but I wasn't. I'd already said by 12 that I don't want to go that way. I sort of regret it because the curious thing is that religion gives you so much. I miss not having belief. Still, being Jewish is something that stays with you. I've always thought that."
Escape from that oddness and the cruelty of his prep school came from writing stories for his fellow pupils about, well, escape from the prep school. But the seed of what made him so suitable for keeping Fleming's flame alive was planted in 1963.
"I went to the cinema with my parents and I saw this film and it blew me away. It's sunshine, it's wonderful food, it's Ursula Andress and none of this is my life." The film was Dr No, of course.
"I was already trying to live my life through imagination rather than reality, and this was just fuel."
And then, just as Horowitz finishes describing his seminal Bond experience, something odd happens.
He looks up and his focus falls on something behind me. In the mirror, there's a screen playing some footage from what looks like an old movie.
"Look," says Horowitz, his gaze still fixed. "They are showing Dr No on television at this very moment. That's the opening credits." And just for that moment, he is distant. Perhaps he is back in that cinema with his parents. But, wherever he is, all the troubles of the past week seem to have evaporated.
