Media mogul Rupert Murdoch's Sunday publication the News of the World was shut down this summer (11) after it was discovered hacks had illegally gleaned information about headline-grabbing stories from private phone conversations and voicemails from celebrities and politicians.
Reporters had also hacked into the voicemail of schoolgirl Milly Dowler after she vanished in 2002. She was later found dead.
Actor Grant spearheaded calls for a high-level investigation into the phone hacking scandal after learning he was among the celebrity victims and now not only has he got his wish, he has been named a "core participant" by Judge Brian Leveson, who is overseeing the inquiry.
Other key members of the investigation include News of the World publisher News International and the paper's former editor Rebekah Brooks and the Metropolitan Police, which has been accused of bungling the original investigation into phone hacking.
Meanwhile, a parliamentary committee investigating phone hacking will recall News International chief executive James Murdoch. The lawmakers are seeking to determine whether James Murdoch misled them about the scale of the illegal practice at the News of the World in his previous testimony.