By John Pienaar
Chief political correspondent, BBC Radio Five Live
Tony Blair has outlined a raft of plans to extend powers to deport or exclude foreigners who encourage terrorism.
There is a new mood after the bombings, says Mr Blair
This was a hugely significant statement. As the prime minister told journalists "the rules of the game are changing".
What he meant was that balance between civil liberties and security was shifting.
And his statement ushered in a far tougher approach to the extremist Muslim fringe, the preachers and converts to violence.
His opening statement set out a path to more and quicker deportations of foreigners preaching, or justifying, hatred and violence.
A confrontation seems certain on several fronts
That much was widely expected. But Mr Blair announced that the powers, unusually, would be retrospective, covering statements already on record.
That, or more likely the explicit warning that he was willing to change human rights law if the courts object, could in future strain the broad political consensus that has held until now.
The prime minister has set out his plans clearly. Agreements with countries like Jordan, Lebanon and Algeria would be used to show deportees were at no risk of being tortured or killed after being returned.
Judges might object. If so, the Human Rights Act - which governs the implementation of the Human Rights Convention - would be changed to ensure that ministers get their way.
It might well lead to a further challenge in the European Court of Human Rights. But here too the prime minister was adamant. Other countries had succeeded in doing what he was now proposing.
The possibility of derogating, or disregarding elements of the human rights convention were left unstated.
But a confrontation seems certain on several fronts; in the courts, outside Parliament with the human rights lobby and perhaps inside the Commons on the extent of the powers Mr Blair has unveiled.
The Liberal Democrats were always the mainstream party mostly likely to object, and the signs of strain are showing already.
Charles Kennedy, the Lib Dem leader, has issued a statement warning that the Prime Minister "should not count on our support."
He was waiting to examine the detail, but banning organisations, closing mosques and deporting people who visit certain mosques or websites ran the risk of inflaming tensions, he said.
That debate will almost certainly begin in earnest in September, with an early recall of the Commons to debate the legislative changes foreshadowed by the prime minister.
The key to the package is the new climate of recent weeks. As Mr Blair conceded, these powers would have met much stiffer resistance just a few weeks ago, before the London bombings.
As before, the prime minister was at pains to emphasise his desire for Britain's multi-cultural society to continue living at peace with itself.
He reiterated his belief in the right of people from all faiths to preserve their culture and practice their religion.
As ever, Mr Blair was hoping, he said, to strike a balance between freedom and security. But it's plainly a new balance. And the start of what could become a difficult and passionate debate.