Given the acclaim surrounding Sir Salman Rushdie's second novel Midnight's Children, it is surprising a film adaptation hasn't happened sooner.

After it was published to Booker Prize-winning success in 1981, the passion surrounding Rushdie's work was overshadowed by the controversy over the publication of his fourth novel, The Satanic Verses, in 1988.

"I think one of the reasons why this film wasn't made before is that there was a long period in the aftermath of the fatwa against The Satanic Verses where it was probably difficult to make a film associated with anything I had done," the writer suggested while promoting the film version of Midnight's Children during the London Film Festival.

"It created a sort of wilderness of a dozen years or more during which it wasn't possible to make the film – it affected not just The Satanic Verses but anything else."

The fatwa was issued in 1989 by Ayatollah Ruhollah Khomeini, the Supreme Leader of Iran, and accused Rushdie of blasphemy. It prompted death threats, forcing the author into exile.

The path back took time. But now Rushdie, 65, has not only been able to revisit his past work but also to serve as executive producer, screenwriter and narrator of Midnight's Children, something he would never have dreamt of doing in his younger years.

He credits the length of time involved to making this possible. "I think one of the things that allowed me to be the scriptwriter was the fact there was such a long gap. I think if it was a book I had just written, I would not have done the adaptation and I would not even have been the best person to do it.

"But because this was my younger self and I could go and look back at what that guy did all those years ago when nobody knew who the hell he was ... There were moments when I looked at it and thought, 'Gosh, that's good'. But there were other moments when I thought, 'Not so much'."

Midnight's Children follows India's transition from British colonialism to independence as seen through the eyes of Saleem Sinai, an individual born at the exact moment when India became an independent country. It is an epic story spanning several generations and many characters, which also draws on Rushdie's penchant for magical realism.

Hence, the challenge was always going to be finding the right person to direct the film and perfecting the balance of the real and the magical, as well as condensing the story into something audience-friendly.

For the director, Rushdie turned to acclaimed Indian filmmaker Deepa Mehta, of Water fame, having first been introduced to her while stepping in for American television talk show host Charlie Rose in 2005.

"Charlie Rose was unwell and I had to sit in for him and I got the job of interviewing Deepa for Water. We gradually got to know each other better and then we talked about sometime working together, and she eventually asked about Midnight's Children. I could see her passion for the story and that it felt personal to her. And I think people direct good films when they feel personal to them, not because it's a famous book or something."

At that stage, Rushdie assumed he would only be giving over the rights to the novel, but Mehta encouraged him to adapt his own screenplay.

"I said to Salman, 'Let's go away and write separately what we think the narrative flow of the film should be'. And we got back together two weeks later and lo and behold they were very similar," she said during the same press tour.

For Rushdie, this was the reassurance he needed to be able to focus on the wider complexities of condensing his work.

"The novel is quite deliberately digressive. It's always going off in all sorts of directions and telling all kinds of stories, but with the film you have to be clearer about the line you're following through. So of course there are things I feel sad about losing."

But the author makes no apology to die-hard fans of the book who may feel saddened to see certain characters or scenes absent.

"If you look at the film of The English Patient, the novel is much more focused on the character of the Sikh bomb disposal expert and the nurse – not so much on the English patient. But I think [author] Michael Ondaatje was OK about it because he felt it worked cinematically.

"And the simple fact is: the book hasn't gone anywhere. So, if there are scenes you like, then go read them."

What about the decision to narrate the film too? "I originally sent an email saying, 'We'll try it, but if we put it on the film and it sounds amateurish then I'll fire myself and we'll find an actor.'"

But Rushdie is happy with the way it and the rest of the film turned out, and was buoyed by the reaction to it from audiences at film festivals.

"I've told a couple of times the story of this gentleman who was sitting next to me when the first screening had taken place at Telluride. When the lights came up he had tears on his cheeks and I said, 'I'm sorry I made you cry'. But he said 'No, these are tears of beauty'. And I thought: 'What could be a better review for a film?'"

Does he expect more adaptations of his work to follow? "I won't expect the floodgates to open yet," he laughs. "But I don't think all of my books are actual movies. Haroun And The Sea of Stories, maybe, and The Enchantress of Florence. But I was lucky in this case to find a fellow creative artist who had a passion for the thing. And I've always thought my books were going to happen in that way rather than big studios coming in. I'm not sure these are big studio books. They're too complicated."

Midnight's Children opens in cinemas today.