I've been to hell and back to revive the huge search for Madeleine, says Kate McCann

Friends said she “went to hell and back” to write the book she hopes will find her daughter, recollecting every detail from those first terrifying days four years ago.

She is being thrown back into the global media spotlight as she prepares for the publication of her 400-page memoir titled Madeleine, billed as “the most heartbreaking book you will ever read”.

Friends revealed that GP Kate, 43 spent five months on the book – which goes on sale on Madeleine’s eighth birthday next Thursday – and often broke down reliving her nightmare.

She hopes its launch will be the key to the solution and is using it to appeal to the youngster’s kidnappers to “let her come home”.

“The whole family is undergoing great stress,” said a friend who has been consoling Kate at her home in Rothley, Leicestershire. “Kate’s been in pieces.”

She added: “Not only is the book about her darling daughter, which she never wanted to write, coming out but the family has also had to cope with the emotional fourth anniversary of her abduction.”

The friend said: “Kate is a very private person and doesn’t like being in the public spotlight.

“She only wrote the book because the Find Madeleine Fund set up to search for her daughter was running out of money.

“She has spent the last five months reliving every parent’s worst nightmare. She has only written the book because she feels it could help solve the mystery and could raise millions of pounds for the fund.

“At times it has been heartbreaking but she has tried to keep strong and carried on for Madeleine’s sake. She is now facing a week from hell as the book comes out and she has to do media interviews to keep it in the spotlight.”

The friend said Kate’s six-year-old twins, Sean and Amelie, helped their mother cope.

Family spokesman Clarence Mitchell said: “At times reliving her nightmare has reduced her to tears. But it has also given her a great sense of focus and renewed hope that it could lead to her daughter being found.”

He added: “Kate is writing the book to raise awareness of her daughter’s disappearance and to pay private investigators to continue the search. Ultimately, she is hoping and praying it will lead to Madeleine being found alive.”

Three-year-old Madeleine disappeared from the family’s holiday flat in the resort of Praia da Luz, Portugal, on May 3 2007. Kate and her heart specialist husband Gerry, 42, are convinced the £20 book, to be published worldwide, will help to trigger new leads. They hope sales and syndication deals will raise more than £1million to boost the Find Madeleine fund.

The book was originally due to be released on April 28 but publishers Transworld delayed publication by a fortnight over fears it would clash with the “media frenzy” surrounding the Royal Wedding.

Mr Mitchell said: “We cannot predict if it will be a bestseller but Kate and Gerry are hoping it will sell very well. Every copy sold will assist the search for Madeleine.”

Kate still finds solace in sitting in Madeleine’s pretty pink bedroom twice a day, revealing: “It’s a comforting feeling. We haven’t changed anything.”

She admits she is stronger and her anger – “a horrible negative emotion” – which nearly destroyed her in the months after Madeleine’s disappearance has subsided. She said “The wounds are less raw but the pain doesn’t go away and the anxiety is always there. But I am definitely a lot stronger than a year ago.”

She added: “We’ve got a lot of hope that Madeleine is still alive. The difficult task is trying to find her but whilst there is hope we’ll keep going and will certainly never give up.”

Last Tuesday, the McCanns marked the anniversary with an open-air prayer vigil in their village, attended by relatives and well-wishers. Commenting on the painful experience of writing the book, devout Catholic Kate said: “We pray that it will bring us the result we long for and that not only the book but this whole ordeal and heartache will be behind us before too much longer.”