La Shawn asks what should we do. Rather than a short comment I'm going to make a longish post.
The first thing I'm going to say may sound shocking but it is worth bearing in mind (and it echoes commentary elsewhere). This was a pretty wimpy effort. Four terrorist bombs during peak times killed fewer people than a single derailment in Japan did a few months back. The Amagaseki crash killed 106 people, the four bombs appear to have killed a little over 50 (at the time or writing it is unclear how many bodies remain to be removed at Russell Square). Clearly we would prefer to have 0 terror victims but, compared to recent disasters such as the Amagaseki crash or the semi-regular Bangladeshi ferry capisizes, let alone the Boxing day tsunami, this wasn't a major incident in terms of fatalities. Indeed to put into context, almost certainly more people were injured or killed on British roads (some of the safest in the world by the way) during the last 30 days than were injured or killed (respectively) by the terrorists, or to put it another way the Swiss bus that fell into a ravine in April killed more people than the terrorists did on the bus in London. Hence there is quite a good argument that says that actually in terms of local defense there isn't much more we should be doing. And to put it bluntly most "high tech" solutions such as biometric ID cards or CCTV cameras everywhere aren't going to help prevent these attacks, and although it is possible that the latter will help catch the perpetrators, almost certainly standard forensics and human informers will be the most valuable sources of information.
There are however clearly a number of things that we shouldn't be doing, and one of them is to cover this event for more than a couple of days. The terrorists don't deserve any more attention than we would pay to a plane crash or ferry capsize in the Philipines so stop giving them the oxygen of publicity. Likewise stop giving time to the "culpa nostra" crowd loads of airtime and do be consistent and call these events and their perpetrators by the right names - e.g. terrorist attacks and mass-murderers not "militants" or "extremists" - oh and don't try and go back on the T word quietly once you used it either.
The "culpa nostra" lot talk about "root causes" and they are in fact correct, we do need to address the root causes of Islamofascist terrorism. However the root causes are not Iraq, Afghanistan or Palestine, they are the poverty and tyranny in the Arab world (primarily) and the generally uneducated and unemployable immigrants in Europe, not to mention the general unwillingness to challenge those who spread hatred of the west from within. This means that actually the invasion of Iraq was the right thing to do and the correct next steps are the encouragement of revolution in surrounding tyrannies. Likewise instead of paying unemployment benefit to the uneducated we let them find a job or starve. Either they die of starvation or they get a job and as a result begin to earn some self esteem, not to mention being too busy to actually plot terrorist acts. In similar vein we insist that mosques (and I'm prepared to add churches, synagogues, shrines, temples...) stop preaching sedition as part of their religion or face the prospect of being razed to the ground and the imam (and the mosque council) deported if not a citizen or put in jail if a citizen after a public trial. I'm not sure whether we need a new law here or not, but I doubt it, I suspect that existing incitement to commit crime laws would apply, perhaps with a minor modification about the laws of property seizure to permit the seizure of the land, destruction of the building and resale of its cleared plot.
In like vein we must insist that the Muslims clean house. We have to promise support to those who stand up to the Islamofascist minority and act on it when they do stand up. This includes, very much, standing up for Muslim women, providing them with shelters where they can flee if need be and with the opportunity to get an education and to get married as they please. Once fairly simple thing would be to ask all youngish women leaving the country to go in a separate room where they will be asked, without the presence of any family member, whether they really wish to leave, and if not provide them with an alternative identity instead. Ditto, in fact for women entering too for that matter. Standing up for and protecting Muslim women will probably kill the Islamic/arabic culture in the west, if not at home. We won't miss it any more than we miss the slave owning culture of the southern US or the cultures of the canibal tribes of Irian Jaya, and we will have a world that is ever so slightly less insane.