The couple have been keeping a low profile recently. What brings them back into the news'

Today marks the fourth anniversary of the day the couple's daughter Madeleine, went missing on a family holiday to Portugal in 2007. While this will be marked in private, the couple will give interviews about the publication on 12 May of the book Madeleine, Kate McCann's account of the disappearance of their daughter. The official Portuguese inquiry into the disappearance was shelved in July 2008, but proceeds from the book will go towards the fund to continue the search for their daughter.

Why are they releasing a book now'

The couple are hoping that the publication of the 384-page book, written by Mrs McCann, will prompt anyone who holds information about Madeleine's disappearance to come forward. The original release date was last week but their publishers, Transworld, postponed this by two weeks to avoid a clash with the royal wedding.

Any other reasons for writing the book'

It also allows Kate McCann to tell her story, after the couple accepted '500,000 in damages from Express Newspapers Group in 2008 for a number of defamatory articles surrounding the case. They are also fighting a legal battle against a former detective, Goncalo Amaral, whose own book, Maddie - The Truth of the Lie, alleges that Madeleine died in the apartment and her parents faked the abduction, an allegation that the McCanns strongly denied. In October the Lisbon appeal court overturned an injunction gained by the McCanns banning the publication of the work.