Video | Murdoch assaulted by shaving-foam wielding activist

Video : Courtesy Channel 4 News

The guardian reports that the perpetrator was sitting four rows back during the proceedings. At one point, he calmly walked up with a plate of shaving foam - smacked it in Rupert's face – when his wife Wendi intervened.

“Wendi can throw quite a punch,” one journalist remarked on Twitter, referring to how Murdoch’s wife intervened to swat away the assaulter.

The individual revealed himself to be Jonnie Marbles, a UK Uncut activist.

UK Uncut is a protest group established in October 2010 to protest against tax avoidance in the UK and to raise awareness about cuts to public services. It uses direct action to get its message across, often closing down high street stores that are owned by tax avoiders.

The parliamentary sitting was paused for ten minutes while Murdoch cleaned himself off and composed himself after the disruptive yet harmless incident.

Earlier, answering questions by UK MPs on the phone-hacking scandal that brought News of the World to a grinding halt, Rupert and James Murdoch revealed the full extent of his ignorance of the phone-hacking scandal at his UK newspaper empire.

In a hesitant performance in front of MPs punctuated by long pauses before many of his answers, the News Corporation chairman and chief executive said it was "the most humble day of my life".

He appeared to have little knowledge of key events and figures who played a prominent part in events that have consumed his company.

Murdoch also shed further light on the nature of his relationship with David Cameron, saying that he had been invited to No 10 but had been told by the prime minister's staff to go in by the back door.

However, when pressed by an MP, Murdoch said his company would cease contributing to the legal costs of Glenn Mulcaire, the private investigator formerly paid by the News of the World to hack into people's mobile phone voicemail messages, subject to contractual obligations.

Rupert's son James, also giving evidence to the Commons culture, media and sport select committee, repeatedly told MPs he was "as surprised as you are" when he discovered "certain legal fees were paid to Mr Mulcaire" by News of the World publisher News International.

James Murdoch, who as News Corp deputy chief operating officer oversees News International, added that the legal advice he was given was that it was "customary to pay co-defendants' legal fees" in civil cases such as the numerous ones the company is facing over phone hacking.

When asked by Paul Farrelly MP whether News International should stop contributing to Mulcaire's legal fees, James Murdoch said: "I would like to do that. I don't know the status of what we are doing now or what his contract was."

Farrelly then asked Rupert Murdoch the same question. "Provided we are not in breach of a legal contract, Yes," he replied.

Earlier in the hearing, questioned by Tom Watson MP, Rupert Murdoch said he was not aware that former News International chief executive Rebekah Brooks had admitted in 2003 that journalists had paid police for information. "I was not aware of that," said Murdoch. "I am now aware of that. I am also aware that she amended that considerably very quickly afterwards."

Watson pointed out that she amended it "seven or eight years afterwards".

Asked why he had not investigated Brooks's comments, Murdoch said: "I didn't know of it. This is not an excuse. Maybe it's an explanation of my laxity. The News of the World is less than 1% of this company, it employs 53,000 people around the world."

Murdoch said he was also not informed about out-of court payments sanctioned by his son James to settle phone-hacking cases involving Gordon Taylor and PR consultant Max Clifford. The News Corp chief said he had "never heard" of Gordon Taylor, the chief executive of footballers' union the PFA.

James Murdoch said his father had only become aware of the payments after they were made public by a newspaper (the Guardian, although he pointedly declined to refer to it directly). He said the level of the payments were "below the approval thresholds that would have to go to my father as chairman and chief executive of a global company".

Rupert Murdoch also said he had "never heard" of the News of the World's former chief reporter, Neville Thurlbeck, who was arrested and bailed earlier this year on suspicion of phone hacking. "That is the first I have heard of that," said Murdoch. "I can't answer. I don't know."

He also said he had not been aware that the culture select committee, in 2009, had accused News International executives of "collective amnesia" about the extent of phone hacking at the News of the World.

"I don't know who made that particular charge. I haven't heard that," he said. "You're really not saying amnesia, you're really saying lying," he told the committee.

Murdoch's performance before MPs today was being seen as a key test of his authority at the head of his global empire amid speculation that independent directors were weighing up the possibility of replacing him as chief executive.

Watson, who turned down successive offers by James Murdoch to take over answering questions on his father's behalf, said he wanted to put the questions to Rupert because he was ultimately responsible for corporate governance at News Corporation.

"It's revealing in itself what he [Rupert Murdoch] doesn't know and what the executive chose not to tell him," added the Labour MP, who has been at the forefront of pressing News Corp for answers over the extent of phone hacking.

Rupert Murdoch said he had visited David Cameron a few days after the general election last year. He added that he was told to go in by the back door and suggested it was "to avoid photographers".

"That's the choice of the prime minister or their staff or whoever," he said. "I was invited within days to have a cup of tea to be thanked for support by Mr Cameron." He added that he had also visited Gordon Brown in Downing Street "many times".

On his relationship with MPs and government, Rupert Murdoch said: "I have never guaranteed anyone the support of my newspapers.

"We had been supporting the Thatcher government and the Conservative government that followed and we thought it had got tired and we changed and supported the Labour party, whatever it was, 13 years ago, with the direct loss of 200,000 circulation," he added.

Asked if he had imposed any preconditions on his support for Labour, Murdoch said: "No, the only conversations I had with them, with Mr Blair that I can remember was arguing about joining the euro."

On Tony Blair's decision to fly halfway around the world to speak at a Murdoch conference, Murdoch confused Alastair Campbell with David Cameron. "That was something Mr Cameron arranged ... Campbell."