As a fan of greater openess in the area of security, I am supposed to be supportive of such an enquiry. But I'm not. Not because of the substance of what it might show us, and the important precedent it would set in the openess stakes. But because of the implied terms of reference.

There is an assumption that a public enquiry will tell us exactly what went wrong - why MI5 did not have the four London bombers on their radar, why they didn't see the plot coming, and what they could have done differently to stop the next one. The words that are being used by advocates on an enquiry are 'clarity', 'truth' and 'closure'.  

But clarity has never been the starting point for agencies like MI5 and Special Branch. The world of intelligence is one of half truths, partial knowledge and human judgements. To pretend that an enquiry will bring clarity to a profession for whom clarity is a rare luxury is nonsense.

Of course, intelligence agencies and governments don't like to admit that's how things work in practice. They like to foster the idea that somebody somewhere knows what is going on and has things under control.

So, as a fan of openess I find myself against the idea of a public enquiry because I think it would be based on a set of false assumptions about the way the state's security apparatus works. And what's more, it would reinforce the idea that the state is in charge and in control.

What we need instead are two things. First, we need some honesty on the part of our politicians and civil servants about how things work. Only then can they be held accountable on the same terms as those in other areas of policy. Political accountability is a rarity in the area of security policy but it shouldn't be.

Secondly, and only if the first is done effectively, we could hold an enquiry, but of a very different nature to that which is proposed or that we are used to. It should be held in the communities from which the bombers came; place equal importance on the testimony of community members, neighbours and friends as of police men, intelligence officers and civil servants. And the terms of reference should not be about finding the 'truth' through a modern day Salem trial, but about working through partial truths together and helping all sides to understand the pressures of the other.   

I understand why so many people want a public enquiry (spurred on I suspect by the fact that politicians have been almost irrationally opposed to the idea). There is a sour taste of secrecy and suspicion left in our mouths by the way these events have been handled. But a public enquiry - on the terms currently set out - will not solve anything and will certainly not help to change the culture that has been built up around our security apparatus (think Iraq dodgy dossier for a similar historical smoke screen)....

The Department for Communities and Local Government (CLG) will publish a new strategy in the coming weeks, which is trailed today in an article by Ruth Kelly in the Observer. Our approach to tackling violent extremism seems to be right at the heart of the approach they are about to start taking.

Think tanks often get criticised for being disconnected from reality and afraid to take on the established status quo (see Henry Porter's attack on the RSA - also on today's Observer comment pages). This is something that Demos definitely cannot be acused of on this one...

We are currently working with the CLG on two projects to develop our approach - first we are launching Bringing it Home locally around the country to get feedback from the communities who helped in our original research. And secondly, we are scoping a framework for diverting young people from violent extremism.