I’m writing this before the big debate which was due yesterday afternoon on the “42 Days” proposal in the Counter-Terrorism Bill.

The House of Lords doesn’t often hit the headlines and it’s usually by voting down a high-profile government proposal. It seems this is one of those moments.

There were some rumours at the weekend that the government would give in without a vote but Gordon Brown is reported to be determined to die in a ditch on this matter.

All the signs are that if 42 days goes to a vote the Government will be well hammered in the division lobbies.

The Conservative and Liberal Democrat opposition parties are united against the idea, there are a large number of unhappy Labour peers including prominent former ministers such as the last Attorney General Lord (Peter) Goldsmith, while many of the establishment “great and the good” on the cross-benches are lined up to vote it down.

The reasons are many and varied, some going back to Magna Carta, notably the principle of “habeas corpus” - you don't “disappear” people without producing them in a court of law to answer a charge.

Other opponents quote practical objections – that by alienating members of Muslim communities, for instance, you may make matters worse – and anyway holding people beyond 28 days is just not necessary.

Magna Carta has a special resonance in the House of Lords.

High up on the walls around the chamber there are huge statues of the Norman barons who forced the hand of King John when they met him at Runnymede 1215.

Of course, this early constraint on the King's powers was mainly in the interests of the barons themselves and England did not become a democracy overnight – arguably that took another 714 years to the introduction of universal adult suffrage (the vote for everyone over 21).

But the charter helped to establish fundamental principle of the rule of law – the King accepted that even he was bound by some legal procedures.

And habeas corpus – the right of appeal of citizens against arbitrary imprisonment – is as important today as it was then.

It’s deeply ironic that it’s the unelected House of Lords – the latter-day barons – that is standing up for these things in 2008.