When Ayatollah Khomeini, the Supreme Leader of Iran, issued the 1989 fatwa against The Satanic Verses author Salman Rushdie, he called for fellow Muslims to send the writer "to hell".

The Iranian government in 1998 quelled the murderous edict (though it was never withdrawn) and the novelist is still very much alive. And yet, in a way, the Ayatollah got his wish — the nine years that he lived under armed guard and perennial surveillance proved a living hell for Rushdie.

"That's true," concedes the 65-year-old author. "From the outside this protection looked glamorous, the armoured Jaguars screeching up in front of the building or the men jumping out and all the doors opening. But actually being on the receiving end of it didn't feel anything like that. It felt like jail. It was very difficult. Things are better at this end of the story."

Rushdie is now in a much better place, literally and metaphorically. Once the fatwa lost its full potency, he embraced a heady social life that carried him to glamorous courts the world over. Professionally, his writing career flourished — he has penned nine novels and two children's book, among other writings — and this year he enjoyed a positive response to the publication of Joseph Anton: A Memoir. Meanwhile, his much-loved second novel, the 1981 Booker Prize-winner Midnight's Children, has finally completed its long and torturous journey to the big screen.

"It is a very unusual time for me," continues Rushdie when we meet in the library of a Covent Garden hotel shortly after the publication of his memoir. It is September's London Film Festival, where Midnight's Children made its UK debut.

"Normally I am a one-thing-at-a-time guy," he admits, "and not good at multi-tasking. I can't ever do two big projects and yet, for the last four years, I really have had to be a multi-tasker, because I have been writing my book and we have been making this film and it has been necessary to go from one to the other. And then, by this kind of miracle, they both appear in the same month, so this feels like a celebratory moment for me."

His memoir, he says, "has been sitting inside me for more than 20 years" while the film of Midnight's Children, "has been to some degree in the making for 30 years. Finally, over the last four years, it has at last made it to the screen." He smiles. "And I actually like it."

Rushdie recalls the moment he saw his friend and fellow author Kazuo Ishiguro in the wake of the premiere of The Remains Of The Day. "And I remember how nice it was that he was so happy about the film. I was happy for him because he was genuinely happy with the film, and I remember thinking if that ever happens to a book of mine, I hope that I end up in that place."

The writer has done all he can to give the film adaptation of Midnight's Children a boost. He worked closely with his friend, Indian filmmaker Deepa Mehta, who directed the piece and insisted that Rushdie write the screenplay. The author also narrates on screen.

"After Salman sold us the option to the book," explains Mehta, who is best known for her Fire/Earth/Water film trilogy, "eventually he agreed, though somewhat reluctantly, to write the screenplay. The problem is length. The book is 533-pages long and the first drafts of the script were 260 pages," which by any filmmaker's reckoning is way too lengthy.

The novel follows the destinies of a pair of children born at the stroke of midnight on August 15, 1947, the very moment that India claims its independence from Great Britain — a coincidence of profound consequence for both. Switched at birth in a Bombay hospital, Saleem Sinai (played by actor Satya Bhabha), the son of a poor single mother, and Shiva (played by Siddharth Narayan), scion of a wealthy family, live out the fate intended for the other.

Imbued with mysterious telepathic powers, their lives then become intertwined and are inextricably linked to their country's tumultuous tumble into nationhood.

Rushdie almost brought the story to life on television with a mooted BBC production, and when he reworked the original drafts he found the process difficult. He had no great desire to put himself through the pain all over again. Mehta, though, was persistent. She wanted Rushdie to adapt the book.

"And I actually quite enjoyed the process in the end," he concedes, "finding that central through-line of the novel that you turn into a workable feature-film script. As an intellectual challenge, as an imaginative challenge, I liked doing it and in the end I am happy to say that I think it worked out. In a funny way I think the film has more up-front emotion than the novel does. The novel is ironized through language and comedy, and the emotion is there but it is sort of underneath. In the film it is there out front."

There is no doubt that an adaptation of Midnight's Children, with its epic blend of history and fiction all sprinkled with a heavy dusting of magical realism, is better-suited to one big sitting on the cinema screen that over five one-hour bites on the television screen. That's particularly true because Saleem and Shiva's telepathic abilities form an important part of the story.

"Television is a medium that has a very difficult time with fantasy, unless it is Doctor Who," explains Rushdie. "Television, certainly in the way in which English television drama has developed, has a very strongly naturalistic quality to it, while the quality of Midnight's Children is that it is a mixture of history, politics and fantasy. It is a mixture of the personal, and to try to get those elements to work on television is very challenging."

Mehta agrees. "Salman's novel is inherently cinematic and very visceral," she says. The author, meanwhile, describes himself as "a movie kid". Like his friend Ishiguro, much of his inspiration comes from the world of cinema. "Movies have always been my real love," he says. "I grew up in Bombay, which is a giant movie city, and I had members of the family involved. I had an uncle who used to write screenplays and I had two aunts who acted in different movies, so movies were in my blood."

The author, who was knighted in 2007, was educated at Rugby School and then at Cambridge University, where he spent many hours in the Arts Cinema, "where the new movies were the new Kurosawa, the new Fellini and the new Godard. I got my education in that little room. The English novel at the time I didn't find very stimulating." He would visit the cinema up to three times a week, "sometimes I would go and see the same film three times a day in order to learn it."

After making the film version of Midnight's Children, Rushdie appreciates more than ever the difficulty of film-making. "It has actually given me a great respect for anyone who gets a movie made, even if it is Porky's 12," he says. In addition to the usual financial and logistical troubles (some scenes involve thousands of extras — and elephants), Rushdie and Mehta also had to contend with the shadow of The Satanic Verses. When filming in Sri Lanka, for example, the production was placed in jeopardy when a communiqué from the Iranian government expressed distress at the shooting of a film based on one of Rushdie's books. Filming was suspended and only after 92 hours of negotiation with the Sri Lankan authorities, prompting a week's delay in production, were the filmmakers allowed to proceed. Controversy, it seems, it never far away.

"We get this word 'controversial' hung round our necks," counters Rushdie. "It is like an albatross. This is just a f***ing movie. It is a movie from a book that everybody loved and we have done our best to make a film that people will love. There is nothing remotely controversial about it, and I wish people would leave it out."

Midnight's Children opens on Boxing Day