An inquiry begins into the behaviour and practices of the press in the wake of the phone-hacking scandal which led to the closure of the News of the World.
In the first part of the inquiry, Lord Justice Leveson will hear evidence on the culture, ethics and practices of the press and its relationship with the police and politicians.
Appearing before the inquiry, which was set up following an outcry over phone hacking at the News of the World, will be alleged victims of hacking including the actress Sienna Miller and singer Charlotte Church.
The notes of the private investigator jailed for phone hacking in 2007 will be summarised and made public as part of the inquiry into the scandal.
Glenn Mulcaire's notebook forms a key part of the ongoing police investigation into the alleged illegal interception of voicemails by the News of the World.
Inquiry chairman Lord Justice Leveson ruled that a summary of the document should be prepared "so that its true significance and extent may be understood".
The Leveson Inquiry has already held a number of preliminary seminars, but it will formally start later with an opening statement from Robert Jay QC, counsel to the inquiry.