Kate and Gerry McCann have signed a deal to write a book about the disappearance of their daughter Madeleine.
After a major bidding war, Transworld won the rights to the couple's account of how the little girl vanished on a family holiday to Portugal in 2007 and their efforts to find her.
All proceeds from the book will go to the McCanns' official fund to look for Madeleine, which had been in danger of running out next year.
The book, entitled Madeleine, will be published on April 28 next year to coincide with the fourth anniversary of the child's disappearance.
Mrs McCann, 42, said: "My reason for writing is simple - to give an account of the truth. Publishing this book has been a very difficult decision and is one that we have taken after much deliberation and with a very heavy heart.
"However, in the last few months, with the depletion of Madeleine's Fund, it is a decision that has virtually been taken out of our hands. Every penny we raise through its sales will be spent on our search for Madeleine. Nothing is more important to us than finding our little girl."
Her husband, also 42, added: "We are hopeful that this book may help the investigation to find Madeleine in other ways too.
"Our hope is that it may prompt those who have relevant information - knowingly or not - to come forward and share it with our team. Somebody holds that key piece of the jigsaw."
