42-days

The Commons is voting on whether pre-charge detention should be extended from 28 to 42 days in terrorism cases.

The reserve powers, which are activated by a "grave and exceptional threat" to the UK, would be subject to a host of judicial and parliamentary restrictions.

But they have still earned the ire of those across the political spectrum, from die-hard libertarians to wary Conservatives.

The vote is expected to be tight but most analysts believe the government will win by a slim margin.

Supporters of the powers say it allows the government to plan for future eventualities at a moment of calm, without the home secretary having to come to parliament after a terrorist attack calling for a state of emergency.

Opponents say it tears up centuries of hard-won freedoms, and gives the terrorists the very achievements they sought to create.