What can be done to prevent further attacks?
Security sources said they believe the four bombers involved in the London attacks were British born and all died in Thursday's bombings.
Chancellor Gordon Brown is to urge EU finance ministers to make greater efforts to target the assets of terrorist groups following the London bombings.
Meanwhile, Home Secretary Charles Clarke is to meet European counterparts to discuss retaining phone and e-mail records to help hunt terrorists.
Are these the right kind of security measures to combat terror attacks? Do they go far enough? How far can we go? Where do we draw the line? Send us your comments.
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This debate is now closed. Read a selection of your comments below.
The following comments reflect the balance of opinion we have received so far:
It's time to do away with complacency and encourage the development of new technologies to rise to the challenge. I do not accept that nothing more can be done to protect the travelling public as some people say. We need our universities, working with the security industry, to undertake a research and development programme to identify new, cost-effective methods of detecting explosives and weapons; methods which could be deployed on the tube without significant disruption. If we are capable of sending people into space, surely this challenge is not insurmountable.
Surely security checks going into tube stations is the most obvious answer to avoid a repeat of last Thursday - no doubt there would be uproar from those who would then not be able to dash through quite as quickly to get a tube, but if it meant a 5 minute delay rather than a bomb, I know which one I'd prefer. We'd work around it, and just get on with life, and continue to use the tube in greater security.
Katherine, Lincoln, UK
100% debit cards not cash. Then all money transactions can be traced - terrorists, common crooks selling on stolen good, and anything else black market would be much harder.
Simon, Birmingham, UK
Terrorists will always find a way to attack the innocent in a free society. If we institute so many checks and curbs that terrorism is no longer possible, then we are by definition no longer living in a free society, and the terrorists will have won. Do we really, as a society, want to be subjected to routine stop and search, have our daily travel delayed and disrupted, and have our private lives monitored?
I think the police and security services need to further strengthen ties with the community. If Islamic fundamentalists did indeed carry out these bombings, maybe joint efforts with the Muslim community would have helped to improve the chances of detection. It would also stop the vendettas that are now needlessly occurring.
Alex, Aylesbury, UK
I strongly doubt that terrorists routinely email each other saying "Shall we plant our bombs today, or wait until tomorrow?" Encryption or even just a lack of plain speaking will mean that email records are almost useless, except as a tiny and easily dismissed source of extra evidence. Phone records are slightly more useful, but we then get into a data management nightmare - look at how stretched the police are looking at 2,500 CCTV tapes, how much more stretched would they be with thousands of mobile records or even fully taped conversations to go through, the vast majority of which will be completely innocent? There must be a better way to target the efforts of law enforcement than this shotgun approach, and that isn't even considering the threat to civil liberties.
Larry, Liverpool, UK
The government should spend the money they are about to waste on ID cards on infiltration and on the ground intelligence about these terrorist groups. There should also be an investigation into how these bombs got through undetected by the security forces.
Justin Tighe, London
The measures that would be most effective, would be to do more to prevent explosives either coming into this country illegally, or if here legally, there should be more powers to ensure that none go missing as happened in Madrid. It is the movement of explosives that should be curtailed not people. Yes they could still produce home made explosives but these are much more bulky.
Phil J, London, UK
Can we combat them at all? How do you fight an enemy who is willing to die to achieve their goals? For every one of them you kill, you just martyr them and spawn a dozen more. I don't have a solution, but I'm quite sure it doesn't involve invading more countries.
John, Southampton, UK
It's hard to see how keeping a log of what numbers my mobile phone has dialled will help anything, especially given the free availability of pay-as-you-go phones which are not registered to any individual and which are topped up with cash payments. Likewise it is useless to try and trace emails since they can be sent from a free webmail account which in turn may be shared by several people at different times. What would also be useful is if the police actually responded to reports of suspicious activity. Some months ago I reported suspicious activity in my area and the police did precisely nothing.
John B, UK
Can we 'combat terror attacks'? Surely if people are hell bent on causing havoc it is nearly impossible to stop them, they will always plan to try and outwit any defences in place, and surely despite all security measures if there is enough attempts at least one will get through.
What concerns me is that civil liberties groups haven't urged a caution on the new terrorism measures that the government will rush through. I was just around the corner from where the bus exploded, and my daily route into work is a constant reminder of Thursday's atrocities, and I do believe that we need to find ways of protecting ourselves from future attacks. However, if we do not watch the government carefully and monitor any changes in law that will affect the civil rights and liberties of all of us here in the United Kingdom, we will have let the terrorists win, because they will have changed our way of life. We must stand united in our support to bring the bombers to justice but we must also stand united in defending our own civil liberties. Once we infringe our own civil liberties, how can we justify sending our men and women to fight for others?
John Lugo, London, UK
All this nonsense that ID cards would have helped either stop the bombings, or identify the victims needs to stop. How many people go on the Tube or bus without some form of identification on them, even if it's only a bank card with their name on? I assume ID cards won't be bomb proof, so what can they do that any other form of ID can't? We need to tighten our border controls and take action to prevent terrorism, such as seizing assets. But we need to tread carefully, there is a line that needs to be drawn here. If we give up our civil liberties then the terrorists, who abhor our way of life and our free democracy, have won.
Lizzie, Doncaster, UK
Too many people leave items unattended. They have no thought for the consequences of this. They should be very heavily fined. After September 11th security was tightened the world over, yet last December I went to Las Vegas with my husband who was on business there. I was to meet my husband at the airport terminal for our flight home. I noticed a man leave what looked like an old kind of sewing machine, a wooden case with a small lead and pedal protruding from it, to join the check-in queue. This was left unattended. Security staff walked past glanced and walked on by! After about 20 minutes I walked over to a security officer and complained, pointed out the man who had left it, he was then spoken to, the security guard walked off and the guy left it against the pillar and joined the queue again! So much for safety, security and being vigilant.
Dianne, North West, England
Democracy and freedom always come with a price. If we are ready to surrender civil liberties for a false sense of security then we are not ready to be free. I'd rather die than surrender my freedom to any government.
Jason Baker, Hull, UK
Targeting the assets of terrorists is one idea that may help if you can get the assistance of every world government and I think we all know this is not going to happen. We should target terrorists with any means available, our security services should be issued instructions to remove these people wherever they may be by whatever means needed, fight fire with fire, show them that attacking this nation was the biggest mistake they could have ever made, they have drawn a line!
Clarke's measures worry me. The cost of implementation will be massive and the scope for misuse within the companies required to keep this information dangerous. Granted content itself is apparently not going to be recorded, but I will still think twice about sending anything plain text, however innocuous. I would like to see the legal framework that will govern exactly what this information can be used for and how permission to obtain it will be granted. Regarding the banking proposals, they would appear to go some way to reducing financial crime generally and should perhaps be looked at further.
Nothing can be done to prevent terror attacks. Our own freedoms work against us and the terrorists know exactly how to exploit the weaknesses in the laws of our democracies. We are not likely to strengthen these weaknesses because people feel that is contrary to democracy itself. It is not. We have to pay a price for our safety and that price can't always be measured in dollars, pounds or euros. Sometimes the price is giving up a bit of our freedom.
William Newcastle, Warwick, New York, USA
Charles Clarke is wasting time and money. What good will retaining phone and email records do? Help catch the culprit post-facto? Well great, but that doesn't do much for prevention, does it? Terrorism is a disease. And like a disease, you cannot cure it by treating a symptom. You have to treat it at the cause. The cause here is the failure of our government's foreign policy. We have to stop believing that we have a right to dictate domestic policy to other nations. We cannot just go on and invade a sovereign country without any reasonable grounds at all (which was the case) and expect there to be no consequences for us. The UK is but one country on this planet, we don't own it. As soon as we accept that, I think out terrorist threat will ebb significantly.
Rory Morty, Giessen, Germany
For me the obvious step forward is funding the police better we already have the knowledge we just don't have the resources. I also think that rail and bus companies need to consider having staff on the trains and buses at all times rather than just a driver that way left luggage can be identified quicker and there will always be someone who knows emergency procedures with the members of the public travelling.
Cat, Cambridge, UK
Why can't the civil police in this country be supplemented in their security duties by the armed forces based in the UK? This would not result in a state of martial law but would send a message to any would-be terrorists that we will take any measures necessary to ensure the safety of our population, regardless of its creed or colour. If our armed forces were based here and not so stretched overseas as they are now, then we would feel much more secure.
Brian Boyd, Barrow in Furness, England
This is a step in the right direction, but as well as acting at an international level, each individual in this country can help. Terrorists need to assume false identities to move around the country. Don't make this easy for them - shred all personal documents, bank statements, utility bills, etc before you bin them.
This is reminiscent of the US reaction to 9/11. I think this idea is premature and is fuelled by a perceived need for our leaders to stand tall and say something comforting. Is it not better to allow our intelligence and emergency services the freedom and opportunity to investigate and see what lessons can be learned? What have we learned from the IRA bombers? These proposals may undermine the opinion of the experts, and could end up being a nightmare to implement. Assets may be difficult in some cases to trace to individual terror groups. They don't come labelled, unfortunately.
Andy Bird, Cheshire, UK
I'm not sure anything can be done to totally eradicate the risk of terrorist activity in Britain. How can you legislate against random acts of senseless violence? However, we can reduce the support for terrorists abroad and at home by having more ethical foreign policies and a more inclusive domestic situation. Certainly, recent attacks on mosques as reported in the papers today will only inflame the situation.
Monitoring potential suspects via CCTV, e-mail or phone tapping may have to be accepted. Closing down London as a centre for terrorism or terrorist supporters including seizing financial assets is also a good idea. The UN should take responsibility for taking action against "renegade" states who support these nutters. Making the issue international and linked to the eradication of poverty is a step all world leaders must surely agree on?
David Burch, London
I don't agree with those people (including senior politicians) who say there is nothing we can do to prevent such outrages. Technology is the answer. If dogs can be trained to detect explosives, then we must be able to invent methods of detection at crucial access points to all public places and means of transport. Of course it would be expensive, but look at the cost of not doing anything.
Mark, Sheffield, England
What a strange announcement. Are we to assume that he is aware that there are EU finance ministers who currently don't give high priority to target the assets of terrorists? If this is the case I think that his message should be a bit more blunt and targeted at the one's who are falling short of the mark.
Trevor, Colchester, UK
You can only get at their assets once you've identified the terrorists - at which point surely you can do more than just close their bank accounts! I have never been convinced that people like this use the world's banking systems to move money around. There are too many trails to cover that way. My belief is that they must use liquid cash as much as possible, for exactly the same reason that tax-dodgers work "cash in hand" - it's virtually untraceable. I have one suggestion for something that could be done: the media could stop telling everyone, including the terrorists, how the authorities are able to track them down. As they used to say during WWII, "careless talk costs lives".
David Hazel, Fareham, UK
I am all for phone records, emails, text records, CCTV footage being kept, but only reviewed in extreme security situations. But I am sure those civil liberty idiots will cause a needless fuss about this as always.
Lee Wilson, London, UK
We are the best eyes and ears of the police. Be alert and report suspicious activity. The government could do better by having more staff checking people entering this country. Currently at the minor London Airports controls are a joke.
Charles Smith, London, UK
I would hope that the British government has the maturity not to go in with guns blazing and blame the attacks on the country which it is most politically convenient to do so. Instead I hope that they build on what they have learnt from dealing with the IRA, to find the people responsible for the London bombings and bring them to justice.
I think the police should use stop and search powers on the Tube. They might not catch the terrorists, but at least they will give them something to think about.
By implementing proper and strict control over who enters our country and actually deporting people who are here illegally!
A Rye, Exeter, UK
One thing terrorists seek is publicity for their cause. Denying them that by refusing to name their organisation until the guilty individuals are named and shamed in the criminal courts would be a start. As counter-publicity, all those killed or injured should - as is done in Spain - be awarded a special decoration to give honour to those who have suffered - positive publicity against terrorists.
Megan, Cheshire UK
I remember hearing that there was a project underway so that mobile phone users could get reception while travelling through the tunnels. Perhaps the underground should put a stop to this and let us all enjoy the peaceful atmosphere us non mobile phone users can still enjoy.
Lee Wilson, London, UK
Unfortunately we are going to have to surrender some of civil liberties, by having more email and phone taping. I don't really care that someone that I'm never going to meet knows something about me, if it saves people's lives. A comprehensive Iraq withdraw plan would also help, because the Iraq occupation could no longer be used as a moral excuse for terror.
Matthew Freedman, London, UK
Loss of funds will severely curtail how they operate. This should have been done years ago.