Prime Minister David Cameron arrived back in Britain to face a grueling parliamentary examination on Wednesday over the phone-hacking scandal, a day after Rupert Murdoch told lawmakers he was not to blame for the crisis.
Cameron returned to London late Tuesday from an African trip which was cut short to allow him to address Britain's lower House of Commons and answer lawmakers' scrutiny over his links to Murdoch's media empire.
Australian-born mogul Murdoch called his appearance before a British parliamentary committee on Tuesday the "most humble day of his life" but his grilling was interrupted when a protester attacked him with a foam pie.
The 80-year-old News Corporation chief's Chinese-born wife Wendi Deng leaped up and slapped the assailant, who was dragged off by police, before the parliamentary committee resumed quizzing Murdoch and his son James.
The attack came near the end of more than two hours of questioning during which Murdoch denied ultimate responsibility for the scandal that forced him to shut the News of the World newspaper.
Appearing frail and at times stumbling to a halt in his testimony, he did however apologise to the victims, saying at the outset: "I would just like to say one sentence. This is the most humble day of my life."
The scandal has rocked Murdoch's global empire, forced two of Britain's top police chiefs to resign and placed Cameron under pressure.
Murdoch said it was "not an excuse" but that with a company of 53,000 staff he could not be blamed for failing to uncover the scandal.
Asked whether "ultimately you are responsible for this whole fiasco", Murdoch tersely replied: "No". When pressed over who he blamed, Murdoch said: "The people that I trusted to run it and then maybe the people they trusted."
But he said he was "absolutely shocked, appalled and ashamed when I heard about the Milly Dowler case two weeks ago," referring to a murdered teenager whose phone was allegedly hacked by the News of the World.
Murdoch also said there was "no evidence at all" the newspaper targeted 9/11 victims, a claim that has sparked an FBI investigation in the United States.
However, his son James Murdoch admitted News International had paid the legal fees of Glenn Mulcaire, a private investigator jailed in 2007 when the hacking at the paper was first exposed.
Around two hours into the hearing, a man in a checked shirt jumped up and attacked Murdoch with a plate covered with foam.
The Guardian newspaper and Sky News named the attacker as comedian "Jonnie Marbles". In a Twitter message shortly before the incident, he said: "It is a far better thing that I do now than I have ever done before #splat."
Scotland Yard later said that a 26-year-old man, later fully named by Sky News and the Guardian as anarchist activist Jonathan May-Bowles, was arrested "on suspicion of assault after an incident during a public meeting", and he remains in custody.
Opposition Labour party chief Ed Miliband prepared Wednesday to turn up the heat on Cameron over the leader's links to Murdoch's empire and apparent reluctance to face the crisis.
Cameron's Conservative party admitted that his former media chief Andy Coulson, himself an ex-News of the World editor, had received "informal advice" before elections last year from Neil Wallis, a key suspect in the hacking row.
Wallis was Coulson's deputy at the tabloid. Both men have been arrested for suspected hacking, and Cameron has faced opposition calls to apologise for hiring Coulson, who left Downing Street in January.
Wallis, meanwhile, is also at the heart of allegations that forced Scotland Yard chief Paul Stephenson, Britain's most senior police officer, and anti-terror chief John Yates to resign within the space of 24 hours.
Stephenson quit after it emerged the force had paid Wallis for public relations work while the paper was under investigation, and also took a free break at a spa where Wallis was a consultant. He denies all wrongdoing.
During a Home Affairs Select Committee hearing on Tuesday, Stephenson said police had been advised by a Downing Street official -- later identified by Cameron's office as his chief of staff Ed Llewellyn -- not to brief the leader on the scandal.
In a 2010 email to Yates, Llewellyn said he "didn't think it would really be appropriate" for the police to discuss the issue with Cameron, and that he "would be grateful if it were not raised".
A spokesman for Britain's Cabinet Office, which is responsible for supporting the prime minister and cabinet, said Tuesday that Cabinet Secretary Gus O'Donnell had seen the emails and "believes that the chief of staff acted entirely properly."
Rebekah Brooks, who resigned as News International chief executive on Friday and edited the paper when Dowler's messages were allegedly hacked, also testified to Tuesday's committee.
She said the hacking of Dowler's phone was "pretty horrific and abhorrent" but insisted she had no knowledge it had happened until papers obtained from police by lawyers for actress Sienna Miller, another hacking victim, emerged in 2010.
Brooks, 43, was arrested and bailed on Sunday on suspicion of hacking and bribing police.
News Corps shares steadily climbed in New York trade Tuesday, recovering 5.51 percent to $15.79 by the close of the markets.