The man who attacked Rupert Murdoch during his parliamentary appearance has been identified as Jonathan May-Bowles, a protester and standup comedian.

May-Bowles dramatically intervened in the committee hearing when he tried to throw a plate of white foam into Murdoch's face at close range.

He was quickly identified by friends in the UK Uncut network of activists. Although the activist group quickly distanced themselves from the protester, he is known to have been a key figure in their campaign.

"This was a lone-wolf, solitary action," said a key organiser in UK Uncut, a tax-avoidance campaigner group. "None of us knew anything about this. This has got nothing to do with UK Uncut."

However, May-Bowles is known to be among the small, close-knit group that founded UK Uncut last year.

Remarkably, the activist, who also uses the name "Jonnie Marbles", appears to have live-tweeted his assault on Murdoch. "I'm actually in this committee," he tweeted at 15.01pm, around 30 minutes into the hearing of the department of culture, media and sport committee.

At 16.51pm, seconds before the attack, he tweeted: "It is a far better thing that I do now than I have ever done before #splat."

Murdoch's wife, Wendi Deng, leaped up to defend her husband and appeared to hit out at May-Bowles with an open hand as security guards and police rushed across the room to apprehend him. The attack prompted gasps in the audience and the temporary adjournment of proceedings.

May-Bowles, who studied at Royal Holloway University, was led away by police in handcuffs.

In a YouTube video he posted of himself last May, May-Bowles talks about why he was going to boycott the general election in his Windsor constituency.

An activist friend said May-Bowles was arrested at a BHS department store for blowing a whistle during a UK Uncut event in December 2010.

He also runs a blog called 'Anarchish' which has as a strap line: "Because the state's not gonna smash itself."

Some friends and associates said they were not surprised he had targeted the media mogul in the midst of one of the most high-profile parliamentary appearances in decades.

A university friend who asked not to be identified said: "He is affable, but very politically minded. He has been a standup comedian for some time, which would explain the custard pie incident with Rupert Murdoch, if that is what it was."

He recalled a time when Marbles complained about the News Corp CEO's influence. "I remember one time he talked about Murdoch. He said it was a terrible thing for democracy that one man should hold so much sway."

He added: "Jonnie is such a devoted activist. I was shocked initially but then I thought: 'That's John.' It was typical but surprising."

The university friend said he was at the UK Uncut occupation at Fortnum and Mason in March, and believed that Jonnie accessed the building.

Another UK Uncut activist said: "He's very committed politically. I know him from working on a variety of different political causes. He was angry about the whole Murdoch thing, how we've got a very powerful elite in this country.

"He works on a lot of different causes. He's got a lot of time for people and he is sort of well respected and liked. He's not a lone figure – he's well known."

He added: "I'm amazed he got in there. He seems to have timed it just as the committee was becoming quite a cosy affair ... Johnny would have timed it. But I had no idea it was going to happen and I was shocked."

May-Bowles is involved in a political comedy in Camden, north London, called Lolitics.