Mr Davis piles on the pressure

For Gordon Brown this was a Pyrrhic victory. Whatever the detail of any deal, last night's vote was preceded by frantic negotiations with potential rebels and supporters, including a number of sweeteners for Labour MPs which contrived to make a bad measure even worse. The Prime Minister's elevated rhetoric about national security was belied by the reality of political horse-trading. And for what? There is no consensus among heads of intelligence, senior police commanders and judges that a 42-day limit is necessary. Further, the safeguards built into the measure to ensure it will be used only in extreme circumstances mean it will be all but unworkable. Moreover the Bill is now likely to fall in the Lords.

But for that reason, many Tories may wonder why Mr Davis has taken such an unprecedented step. Certainly he is taking a courageous and principled stand, which promises to reopen the debate on the anti-terror laws. But his one-man campaign is already highlighting differences in opinion between shadow cabinet members like Mr Davis, who take a more libertarian view of such state power, and those who incline to a more pragmatic approach on a security issue where the majority of public opinion is behind the Government. David Cameron does not appear to be happy with Mr Davis's move, and nor are other senior Tories.

The Prime Minister has done his credibility no good with last night's scramble for votes - or with his denial today that he did any deals. Now the challenge for the Conservatives will be to keep up the pressure on him. It remains to be seen whether Mr Davis's resignation will create divisions in the Tory ranks.