Prime Minister Tony Blair has lost the key House of Commons vote on plans to allow police to hold terror suspects without charge for up to 90 days.
MPs rejected the plans by 322 votes to 291 - a bigger than expected majority of 31. It is Mr Blair's first defeat since Labour came to power in 1997.
The defeat will be seen as a blow to the authority of Mr Blair, who said MPs had a "duty" to support the police.
Labour has a majority over other parties of 66 but the defeat does not mean Mr Blair will have to stand down as prime minister - something he has said he will do before the next election.
Liberal Democrat frontbencher Simon Hughes said the defeat marked a "momentous day" which could bring forward Mr Blair's departure from office.
"It was a major error of judgement and it undermines Mr Blair's chances of staying on," said Mr Hughes.
This is very good news, almost as good as Blunkett's resignation. I would like to be erudite about this but, at this moment in time, I'm afraid that I can only find one reaction to the news.
UPDATE: It's limerick time again! Here's my off-the-cuff effort...
There was a fascist Prime Minister,
MPs thought his Terror Laws sinister.
Blair pushed his luck,
They said "Get tae fuck!"
With any luck, now he'll leave Westminster
Hem-hem, poetic license, don' cher know...
Feel free to add more in the comments!
*Now to find out how my MP voted, Labour lickspittle that he is...