A protester interrupted Tony Blair's testimony at the Leveson Inquiry on Monday, shouting: "The man is a war criminal!"
The intruder, a white male in his 40s, was forcibly removed from the room after entering through the non-public part of the Royal Court of Justice.
Before being wrestled out of the room, the protester shouted: "This man should be arrested for war crimes... JPMorgan paid him off for the Iraq War... three months after he invaded Iraq he held up the Iraq bank for £20bn. He was then paid $6bn a year by JPMorgan and still is... the man is a war criminal."
After the incident, a man identified himself to reporters as David Lawley Wakelin from the Alternative Iraq Enquiry. He spoke as security guards escorted him through the Royal Courts of Justice.
It is understood the protester, who burst into the hearing directly behind Lord Justice Leveson, managed to get past security-coded doors to access the judges' corridor leading to courtroom 73. He was subsequently arrested and released without charge.
Following the incident, a different protester threw an egg at the former PM's car as he left the inquiry, according to reports.
Lord Justice Leveson has ordered an immediate investigation into how the man gained access.
He said: "I would like to find out how this gentleman managed to access the court through what's supposed to be a secure corridor and I'll have an investigation undertaken about that immediately."
Blair remained calm throughout the disturbance.
After the removal of the protester, Mr Blair denied his allegations.
He told the hearing: "What he said about Iraq and JP Morgan is completely untrue.
"I've never had a discussion with them about that."
Even Robert Jay was lightly ruffled by the intruder
A spokesman for Her Majesty's Courts and Tribunals Service said the Service took security very seriously at all of their venues.
"An investigation has been ordered into an incident at the Leveson Inquiry, Royal Courts of Justice, today.
"It would be inappropriate to pre-empt the findings of this investigation," he added.
When the hearing reconvened for the afternoon, Lord Justice Leveson told the court the Inquiry and HMCTS took the incident "extremely seriously" and apologised for the breach.
He said: "Considerable effort has been put into ensuring all witnesses can give their evidence in a safe and secure environment and I very much regret what has happened.
"An investigation is being undertaken and I will be giving consideration to the steps that can be taken and should be
taken against this particular intruder.
"Efforts will be redoubled to ensure that incidents of this nature don't recur.
"I repeat my apologies to Mr Blair and indeed to everyone else who was involved in or following our inquiry."
Earlier, Blair said he felt the power of the British media was unhealthy while he was PM - but chose not to take it on as it would have prevented him from pursuing any other policies while in power.
On arriving to give evidence at the inquiry, the former PM had been greeted by around two dozen or so protesters as he arrived at the courts this morning.
They waved banners reading "Troops home", "Bliar" and "Afghanistan out".
A man, reportedly David Lawley Wakelin, was led away from the Royal Courts by police
28/05/2012 15:18 BST
That's it, the end.
Blair's time in front of Leveson has come to a close. Towards the end it was less of a grilling more of a cosy fireside chat.
Join us tomorrow when we will hear from education secretary (and former Times journalist) Michael Gove and home secretary Theresa May.
28/05/2012 15:07 BST
Lord Justice Leveson just asked Blair what may have been the longest question ever asked. The line that will come as a relief to many was "I have absolutely no interest in imperilling the freedom of the press".
28/05/2012 15:01 BST
Tom Watson responds
Tom Watson has posted a quick response on his blog to Blair's answers about his resignation. You can read it here:
28/05/2012 14:59 BST
Protester led away
Here is a picture of the protester, named as David Lawley-Wakelin, being led away by police.
28/05/2012 14:50 BST
@ BBCNormanS :
TB extolling the virtues of US papers over UK press. Er..but have u read them ? Dullsville Central #leveson #blair
28/05/2012 14:49 BST
Blair is comparing the British media to the US media. He says American papers are capable of having a editorial line while at the same time reporting the "facts" as facts.
The collective response from many British journalists on Twitter is to argue that US papers are "dull".
28/05/2012 14:43 BST
Blair has moved on to talk about the nature of news in an era of Twitter and 24-hour news channels. He says there is a "race to the bottom" which is damaging to the political debate.
"These guys have got to say something and they just say the same thing they were saying a few moments ago," he observes.
28/05/2012 14:34 BST
Blair says one cabinet minister once came to him to resign as he had read in the newspapers that he was going to be sacked.
He says he had to spend half an hour persuading him that he was never going to be fired in the first place.
28/05/2012 14:25 BST
Blair says he sometimes made ministers resigned even though they had done nothing wrong as the press coverage was becoming too damaging.
He specifically cites the second time Peter Mandelson was forced to quit the government.
28/05/2012 14:18 BST
Blair: I was going to fire Watson
Tony Blair is asked about Labour MP Tom Watson, who resigned from his government after calling on him to resign.
"I was prime minister, he had effecievely taken part in the coup in 2006 against a prime minister," Blair says.
Blair says Watson resigned "literally moments" before he fired him. "You can't remain a minister if you called for the PM to go"
Blair says that his allies wanted to "go on the attack" but he said he decided he would have to announce when he would leave No.10 in favour of Gordon Brown.