Kate and Gerry McCann have arrived to give evidence to the Leveson Inquiry into press standards about their experiences of the media after their daughter Madeleine went missing.
The couple are expected to describe their anger at newspaper stories suggesting they may have been involved in the little girl's disappearance from the family's holiday flat in Portugal in May 2007.
The McCanns, from Rothley, Leicestershire, have previously spoken of their frustration that negative reporting like this was distracting from the search for Madeleine.
The inquiry, sitting at the Royal Courts of Justice in central London, will also hear evidence from Sheryl Gascoigne, the ex-wife of former England footballer Paul Gascoigne, lawyer Mark Lewis, who represents phone hacking victims, and journalist Tom Rowland.
Comedian Steve Coogan on Tuesday claimed he was the victim of two "sting" operations by the News of the World. He told the inquiry that the paper's former editor, Andy Coulson, secretly listened in on a phone call designed to entice him into revealing personal information.
Mr Coulson, who became Prime Minister David Cameron's communications director, was also accused of using a surreptitious recording of another call to Coogan to betray a promise to omit "lurid" details about the break-up of one of the star's relationships.
Coogan told the inquiry that tabloid newspapers were "like the mafia" and said other celebrities feared being victimised by the media if they gave evidence to Lord Leveson's hearings.
The inquiry will hear on Thursday from actress Sienna Miller, Harry Potter author JK Rowling and former F1 boss Max Mosley.
The first part of the Leveson Inquiry is looking at the culture, practices and ethics of the press in general.
The second part, examining the extent of unlawful activities by journalists, will not begin until detectives have completed their investigation into alleged phone hacking and corrupt payments to police and any prosecutions have been concluded.