Frederick Forsyth signed up to write sequel to Phantom of the Opera

The Day Of The Jackal author is collaborating with the musical impresario for the story of Phantom Of Manhattan, set 20 years after the original.

Sources close to Lloyd Webber confirmed he would be working with Forsyth, whose background as a thriller writer does not make him an obvious candidate to pen a romantic musical.

The two men are believed to have met several times in the past few weeks to discuss the intricacies of the plot, which sees the Phantom leave Paris to build a new life in New York. The musical will be partly based on Forsyth's book of the same name, published in 2000, which takes further the story of Erik, the phantom who wears a mask to hide terrible disfiguration.

Forsyth's book was unpopular with some fans, who felt he had not shown sufficient reverence to the original work by Gaston Leroux.

Lloyd Webber said: "It's taken me ten years to decide to do this and I want to base it on the ideas I had with Freddie Forsyth years ago for something called The Phantom Of Manhattan that came out as a book.

"There are various things in the plotting that I'm not very happy with and I think I've solved them. I hope we can sort them out but I'm really pretty buzzed up about it."

Lloyd Webber's original musical has made £1.7billion since it opened in October 1986, with Michael Crawford and Sarah Brightman in the lead roles. There have been more than 17 productions around the world, which have been seen by 80million people.

It has been a massive hit in the United States and setting the new musical in Manhattan is likely to appeal to American audiences.

In the original, Erik wreaks terror on the Opera Garnier in Paris in 1881. He falls in love with a junior soprano, Christine, and tries to steal her away from Raoul, her childhood sweetheart.

Forsyth's sequel describes the story of the Phantom after he travels to New York to make his fortune, building the Manhattan Opera House so he can see Christine again. She is now a famous diva and has a son by Raoul called Pierre.

Forsyth, 69, said in an interview that the novel came about after he had dinner with Lloyd Webber.

"He said to me, 'You know, one thing that's always intrigued me is whatever happened to this guy?' I began to think, intriguing idea, a lot of problem solving, a lot of working out what could have happened, might have happened. It must have ended, something happened, the guy went somewhere, he did something - he lived."

Lloyd Webber will start work on the new Phantom after he has finished his BBC series Any Dream Will Do, which searches for a new star for Joseph, another of the 59-year-old's successful musicals.