This is how it happened, minute-by-minute, from politics.co.uk's live updates.
Home secretary Jacqui Smith began outlining the government's plans after a stormy prime minister's questions, in which Gordon Brown faced attack from all sides of the House over the 42-day issue.
"The government believes that such a reserve power should be available for us if necessary to protect our national security and to protect our people against the threat we face from terrorism. That threat is real and it is serious," she told MPs.
Ms Smith constantly gave way to MPs on various aspects of the bill, including compensation for those who are not charged after being held for 28 days, the definition of what constitutes "grave and exceptional" circumstances and why she has avoided judicial review of the decision.
The Speaker stood up in Ms Smith's favour for the constant interruptions, which he describes as being "unfair in many ways".
She outlined the many concessions made by the government, saying "our amendments reinforce the temporary nature of the power". These include individual detention beyond 28 days being considered by a judge, the director of public prosecutions, and scrutiny of positive decisions by an independent reviewer and parliament.
"We have talked, we have listened, we have moved," Ms Smith insisted.
Shadow home secretary David Davis argued the government has not made its case about the necessity to extend pre-charge detention beyond 28 days. He said previous major terror cases saw all evidence available within four and 12 days - and that Ms Smith evaded his questioning about this during consensus meetings as a result. The proposal, which takes "the worst of all worlds", is "wrong in principle and flawed in practice", he argued.
"We do not defend our liberties by defending our liberties and we must reject the government's proposals," Mr Davis concluded.
Keith Vaz, chairman of the home affairs select committee, explained his committee's finding that there is "no evidence" backing up the government's stance. He said it would be better if the Civil Contingencies Act had been amended but added "we are not there yet".
Despite his committee's conclusions he said he would back the government on 42 days because "it is an emergency temporary provision" containing "guarantees" protecting civil liberties.
Liberal Democrat home affairs spokesperson Chris Huhne described elements of the bill as "frankly Kafka-esque" and warned parliamentary scrutiny did not amount to a "serious check on the potential abuse of executive power".
"The fight against terrorism is far too important to be reduced to populist symbols which would substantially curb our hard-won freedom," he said.
"The government runs the risk with these provisions of giving the terrorists exactly what they want which is clear evidence of an insensitive and oppressive state. We must not and we must never become what we are fighting."
Andrew Dismore, who has tabled amendments on the bill, argued the government had not made its case and said the proposals will not make ordinary Britons any safer.
Menzies Campbell, former leader of the Liberal Democrats, made his case against the plans.
"I will vote against the government," he stated proudly.
Veteran Labour rebel Diane Abbott continued his line of argument.
"I won't take lectures from ministers about not taking terrorism seriously," she said.
"They may win the vote, but they have emphatically not won the argument."
Ms Abbott expressed her irritation at the fact the issue had come back to the Commons just two years after it was last debated.
"The police are split on this," she stressed.
"Don't vote for the government on the basis of a shoddy compensation package," she urged - citing the extra sweetner offered by the government this morning.
"Any rebel backbencher with a cause" has been given assurances in exchange for their support," she continued.
"It is a test of parliament that we are willing to stand up for the liberties of the marginalised," she said, in an impassioned section on supporting the Muslim community while it comes under daily attack, in her words, by the mainstream press.
"It's my constituents we're talking about," the MP for Hackney said.
"I didn't come into politics to vote for this sort of stratagem. Of course the public is in favour of this, but if we as a parliament cannot stand up on this issue, then what after all is parliament for?" she asked.
Backbench Conservative David Davies stood up to talk, but prefaces his comments by saying Ms Abbotts speech was the finest he ever heard in the House.
Martin Salter, Labour MP and member of the home affairs committee, stood up to speak.
He went on to make the case for the reserve powers, calling on MPs to let it be worked out now, rather than in the panic of a series of terrorist strikes.
John Baron, Conservative MP for Billericay, stood up to argue against the plans.
He put the government arguments against the comparability of other country's detention systems under a lot of scrutiny and found them lacking, not least of all because the government has conducted no research on the subject.
The leader of the SDLP, Mark Durkan, said the plans will make the Commons act "in the role of a grand jury".
He raised the point that terrorists could deliberately organise for the police to find evidence, simply to put Britain into an effective state of emergency and thereby raise the stakes in their war against the country - especially during an election.
"What situation does that put MPs in?" he asked.
"We will see communities being fundamentally alienated from the state," he argued, nearly at the point of shouting.
"Do not feed what you want to fight," he urged his parliamentary colleagues.
Liberal Democrat David Heath took over. He called the plans unjustified, unworkable and unhelpful.
With less than half an hour left before the vote, MPs knew no-one inside the chamber was being convinced of anything - despite the almost unprecedented passion and rhetorical strength of the speeches being made. All the real action was taking place in the secretive corridors of Westminster, and especially in Gordon Brown's office, where rebel Labour MPs were being ushered to receive promises about their particular issues.
Labour man Frank Cook said he received a text from a constituent, the only one to support the plan, asking him to support the government or else he would put his marginal constituency at risk. But the debate should not be about marginals, he said, because it is a matter of principle.
The big hitters came back into the chamber, with Jacqui Smith and the Tory front bench back arguing about the plans.
"I cannot and will not wish away the threat from those whose sole intent is to blow away our citizens," she argued.
"However important consensus is, I prize the security of Britain above it."
The debate then came to an end, with MPs preparing to vote.
Reports of DUP members standing in the government lobby, indicated a government win.