It's a pity that this thread seems to be slipping into an attack on bjcc's intelligence, or lack of it, with the implication that his is a typical unimaginative, unintelligent approach of the average police officer.
During my fairly long life I have had quite a lot of close contact with police officers in a professional situation. I can assure those that talk about stupidly woodentop comments and and you like to always have the last word, as it is typical of those in your position, just to cite two random examples of apparent generalisations, that I have encountered many police officers who are highly intelligent, open-minded and possessed of a knowledge of the world and its citizens far greater than the average person.
I have read many of bjcc's posts on other topics and he clearly has a first rate knowledge of the criminal law and its application.
Having said that, I don't agree with bjcc that the economy argument doesn't hold water. Others have already accurately put the counter argument so there is no need for me to expound further.
The Home Secretary has said the current security measures are time-limited, but that is a vague concept.
There will always be risk in life and the current battle against terrorism will always be a balance between reasonable precautions and allowing everyone to get on with their lives.
As many people are killed on the roads in the UK each year as were murdered on 11 September 2001, but we don't stop people driving cars. We try to limit road casualties by taking reasonable measures, knowing we shall never be completely successful. The same applies to aviation security.
To comment on FL's point about the rank of constable, it is somewhat anomalous in that every police officer is sworn in as a constable and exercises his/her powers as a constable, but that some Acts of Parliament give additional powers only to police officers of a certain rank, eg the Police and Criminal Evidence Act gives inspectors and superintendents powers to authorise searches under various scenarios.
For many years police ranks were primarily for internal discipline and administration, but we seem have gone far beyond that in 21st Century Britain.