A Fathers 4 Justice campaigner has been released on police bail after scaling the Houses of Parliament for a protest.
Guy Harrison, 38, spent five hours on top of Westminster Hall, bearing a banner which read "Does Blair care?".
Mr Harrison, of Ashurst, Sussex, eventually climbed down at 2000 BST on Tuesday and was arrested on suspicion of aggravated trespass, police said.
In 2004 the fathers' rights campaigner staged a protest at the Commons, when he threw flour at Tony Blair.
As he was driven away in a police van on Tuesday, waiting supporters clapped and cheered.
A police spokeswoman said Mr Harrison was taken to London's Charing Cross police station for questioning.
He was bailed on Wednesday and is due back before police in October.
Fathers 4 Justice said Mr Harrison's protest had been timed to coincide with Mr Blair's speech at the Labour Party conference in Brighton.
Spokesman Matt O'Connor said Mr Harrison had taken advantage of "lax security" and climbed out of a window with another protester after taking a tour of the Houses of Parliament.
Speaking on his phone from the roof of Westminster Hall, Mr Harrison, a wealthy farmer and entrepreneur, said the protest was "a present" for his seven-year-old daughter who he said he had not seen for more than four years.
"I hope this will remind her how much I love and miss her," he said.
Of the campaign to improve access rights for fathers, he said "We've been in dialogue for nine months with government bodies and we hoped we would receive more co-operation than we have.
"I can't think of anything worse than doing this, it's terrifying - I've never climbed up high like this before.
"I can see armed police down there - that doesn't instil me with a lot of confidence."
John Hemming, Liberal Democrat MP for Birmingham Yardley, called for a security review into how "someone should be able to break security twice".
"I am calling for a review to see whether there can be a technological solution to scan and recognise the faces of those people who have a track record of doing things like this at Westminster," he said.
Leader of the House of Commons Geoff Hoon, speaking from the Labour conference in Brighton, said Mr Harrison had "exploited the opportunity" offered by summer tours of Parliament.
"I'm not in any way minimising the seriousness of the situation, but obviously MPs are not there and ministers are not there... but this is a serious situation and we will look at very carefully," he told BBC News.
"There is always a necessary balance, a judgement to be made between security and ensuring in a democracy that people can see how a democracy works."
Last May's Commons protest, when Mr Harrison threw a condom filled with purple flour, prompted a security review.
Mr Harrison was fined £600 for throwing the missile.
Tuesday's rooftop protest marks the latest in a series of high-profile protests by Fathers 4 Justice.