In the mind of Douglas Adams, the number 42 may have represented the answer to life, the universe, and everything. While it may have taken Adams' computer, Deep Thought, 7½ million years old to compute and check the answer, it appears to have taken Gordon Brown far less time to persuade 9 Democratic Unionists that empowering  police to hold terrorist suspects for 42 days without charge would be in their collective interests. Despite the Prime Ministers' claims to the contrary, it appears that he has ensured their support by agreeing to a string of extraordinary concessions to the DUP, and to his backbenchers, to save the vote, and possibly his premiership.

Brown was accused of trading civil liberties in a "grubby bazaar", accepting a shopping list of demands from the Northern Ireland unionists and offering a range of promises on backbenchers' pet projects, such as compensation for injured miners, increases in rail investment, the accountability of the intelligence services and lifting EU sanctions on Cuba.

Brown had staked his personal authority on winning the vote, but 36 of his backbenchers joined the Conservatives and Liberal Democrats in the No lobby, slashing his theoretical 66-seat majority. In the end, only the support of the nine DUP members, UKIP's Bob Spink and the Tory MP Ann Widdecombe saw the government home by nine votes.

The government and the DUP claimed their discussions centred solely on the principles of pre-charge detention and Northern Ireland's history with internment. The DUP's Rev William McCrae insisted "hand on heart, it was a principled decision based solely on security considerations". But it was privately acknowledged the DUP had also pushed for a financial package to lift the burden of new water charges, speed up asset sales and exclude Northern Ireland from the Abortion Act. The DUP is hoping for a Anglo-American package to be announced when George Bush and Brown visit Northern Ireland on Monday.

A month ago defeat looked highly likely - but Brown's position has become more perilous since then. The humiliation of winning on the back of Democratic Unionist votes, after failing to win round rebel backbenchers, will only add to his troubles. It might have even been better to lose outright. Yesterday parliamentary critics claimed that the party's mood had hardened against Brown, made worse by his insistence on winning a vote almost no one thought needed to take place.

Pre-charge detention reeks of neocon fear and paranoia tactics. It was the Terrorism Act in 2000 that allowed terror suspects to be held for 48 hours, extendable to seven days with the permission of a judge. That was doubled to 14 days in 2003 and doubled again to 28 days in 2006. Now that 42 days is heading to the statute book it can be expected the police will come back again after the next election to press the case for 56 days or more. Other countries that have suffered from terrorist attacks manage with far less. The US has a two-day limit; Spain five days and Turkey seven and a half days.

Where will this madness end?

By Paul Tuthill/MOLI