Milly Dowler's parents will tell the press standards inquiry of the heartbreak they suffered when a private investigator gave them false hope about their missing daughter by deleting messages from her mobile phone.
Sally and Bob Dowler, the first witnesses to the Leveson Inquiry, will also describe how the News of the World intruded on their grief by publishing a picture of them privately retracing the route Milly was walking home when she was abducted.
The trigger for the inquiry was the revelation that the Sunday tabloid commissioned private detective Glenn Mulcaire to hack the murdered schoolgirl's phone after she disappeared in 2002. As well as listening to Milly's voicemails, the investigator also erased some of them to make room for new messages, falsely leading her family to believe she was still alive, the inquiry was told.
David Sherborne, counsel for the Dowlers and other victims of press intrusion, told the inquiry last week that Mrs Dowler felt "euphoria" when she finally got through to her missing daughter's voicemail as a result of Mulcaire's deletions. He said: "Perhaps there are no words which can adequately describe how despicable this act was."
Mulcaire was jailed along with the News of the World's former royal editor Clive Goodman in January 2007 after they admitted intercepting voicemail messages left on phones belonging to royal aides.
Lord Justice Leveson's inquiry will also hear this week from 16 other alleged victims of media intrusion, including Hugh Grant, Sienna Miller, JK Rowling and missing Madeleine McCann's father Gerry.
Grant, who will also appear on Monday, is expected to condemn paparazzi for hounding the mother of his baby daughter. Chinese actress Tinglan Hong was recently granted a High Court injunction prohibiting harassment of her and the child.
Other witnesses will be lawyer Graham Shear and writer Joan Smith, whose phone was allegedly hacked because of her relationship with MP Denis MacShane.
The Leveson Inquiry began its formal hearings at the Royal Courts of Justice in London last week, when it heard that police believe phone hacking at the News of the World had begun by 2002 and continued until at least 2009. But a lawyer for Scotland Yard played down claims that Mulcaire's notebooks suggest that at least 28 journalists from the top-selling tabloid commissioned him to hack phones.
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 concluded.