There are two aspects to this :-
1. The public's fear of Knife & Gun crime.
Many parts of Britain are a less safe place to wander the streets than either the public would want or than other parts of Europe. However, even with the worst reported figures, the risk to innocent members of the public unconnected with knives or guns is very low. Certainly significantly lower than the perception.
2. Arms race between criminals and police.
I don't really see how this can apply when there has been little deterrence to date. Added to which, much of the gun and knife crime is reportedly not committed by career criminals. The police bringing in mobile scanners etc. is not going to stop it but it may have some effect. I cannot see how harder targeting of knife/gun crime and better monitoring can make things worse than they are today.

There is an old saying by an unknown person regarding readiness for uncertain situations, "Better to have it and not need it, then to need it and not have it."
I believe that this saying best explains the situation at hand. It is better to be ready for something which may never occur than to be lulled into a false sense of security and pay for it later.

I still think there is something to be said about displaying heavy arms to the community you patrol — until recently, most police in the U.K. did not carry firearms at all — and about this proliferation that I refer to as "our domestic arms race." But generally, I do agree with you now.
It's called "Policing by consent". In Britain, the police are an independent institution, more closely allied to the courts than to the government. In most other countries, the police are either a paramilitary force, or a defensive arm of the government - whether local, regional or national.
Also, Britain has never had a great tradition of firearms ownership (apart from shotguns and airguns in rural areas), so the police have not had to face armed men on a daily basis.

http://uk.answers.yahoo.com/question/index?qid=20080703033534AATjB7P&show=7