Thanks for your comments, Keith. I'm 'just Joe Public' as well!

As I see it, this is not a case of choosing to do something to prevent terrorism, but doing something that may reduce terrorism affecting, to be realistic, a minute proportion of the population at the cost of not just civil liberties but increased risk of violence to the majority of the population, caused by various groups feeling they are victimised or seen as worth less by the rest of the population.

Putting it in what I admit are probably extreme terms: how do we trade off the risks of more cases like Steven Lawrence against the chances of preventing 7/7s?

It's the uneviable task of Parliament to come to that balance. What I think is a great tragedy of politics, generally, is that once people have come to that difficult decision they feel obliged to present their conclusion without admitting its costs and also disparaging anyone else who came to a different balance.