Tony Benn, the man still regarded as the quintessential Socialist, came to the support of Conservative MP David Davis who is fighting for reelection in defence of civil liberties. Benn asserts that 42 days detention without charge is wrong, the ID database is a monstrosity and Parliament has no right to give away the sovereignty of the people by ratifying the Lisbon Treaty.

Libertarians from the Left and Right sometimes meet in the middle against an authoritarian state. In 1961, having served for 10 years as an MP for Bristol South East, I was declared disqualified because my father had been a peer and he had died. It was argued that I had inherited his peerage.

A by-election was called, and, despite my disqualification, I decided to contest it to argue a point of principle. Winston Churchill, the former Conservative Prime Minister, sent me a letter of support for which I am, to this day, most grateful. I must be the only Labour candidate who has ever circulated 30,000
copies of a letter from a Tory leader to my constituents. The law that prevented me sitting in the Commons was later changed as a result of that by-election.

So when I heard that David Davis was standing in the Haltemprice and Howden by-election, I decided to support him. I hope the Government's move towards 42 days' detention without charge, recently passed in the House of Commons, will be stopped as a result of his campaign.

42 days and Magna Carta

The civil liberties issues on which Mr Davis stands are important to the future of this country. Last Friday I attended a conference organised by Lincoln Cathedral on Magna Carta, an original of which they hold. Magna Carta had nothing to do with democracy, but one phrase in it has registered worldwide: "no man shall be taken [and] imprisoned. except by the lawful judgement of his peers."

For many years the Labour government has boasted about the traditional values and freedoms of this country; and yet, when its MPs voted to amend the Terrorism Act and permit 42 days in prison without charge, they effectively repealed Magna Carta.

Such a law would mean that people could be imprisoned for six weeks, then released without charge or trial but also without ever being properly acquitted: a cloud of suspicion would remain.

It is also clear that anyone released after such a period would almost certainly find their life destroyed, with their job lost and real risk posed to any prospect of future employment.

Stop the huge database of personal information to be collected by the government

There are two other critical ways in which liberties are being eroded, both highlighted by Mr Davis.

The first is identity cards. I have no objection to them in principle, because in the course of my life I have held many cards with my photo, name and profession printed on them. What matters more is the huge database being established in concert with ID cards, on which will be gathered every bit of information that it is possible to collect. It may contain your financial status, political opinions, email contacts and more - no one will really know what is on that database.

Indeed, the information held may be inaccurate. When I recently renewed my passport, I noticed that I am still described as a Member of Parliament. If the Government does not know that I am not an MP seven years after I stepped down, it does not inspire confidence that a more wide-ranging identity database would be very reliable.

The information may leak, and it would be valuable for commercial and other purposes, including fraud and terrorism. Despite the guarantees of ministers, and regardless of whatever safeguards are promised, we know from recent examples that information held by the Government can escape.

The sovereignty of the people which is not in the power of Parliament to give away

Second, the Lisbon Treaty diminishes the sovereign powers of British democracy, which belong to the people and are lent to MPs. MPs have no right to dispose of them to the EU.

The Irish have defeated the Lisbon Treaty democratically, and Britain was denied a referendum on the Treaty only because it was clear that the Government would be defeated on it here.

Because the people are sovereign, governments get their powers from us; we do not get our rights from them. This issue is becoming crucial because the centralisation of power to political elites is a threat to our freedom and democracy.

The Haltemprice by-election is taking place because Mr Davis gave up his seat and possible position in any future Conservative government to seek his constituents' verdict on these issues.

The fact that the Labour party has decided not to contest the seat indicates that it knows that it cannot win the argument on 42 days.

I believe that Mr Davis's stand may do something to restore public confidence in politics and politicians. If, as is expected, he wins, it will confirm the judgment he made on the 42 days and will also destroy the argument that the public really supports these oppressive measures.

If the Lords, as expected, also rejects 42 days, it would be a constitutional outrage to use the Parliament Act to enforce the will of the Commons on the second chamber.

It is on the single, but vital, issue of civil liberties that I decided to support David Davis.

So do we. If you don't have civil liberties, you have nothing.