It seems that the above would also apply to London, yet we manage to get along with a (largely) unarmed police force, so I'm not buying it.

As far as I understand it, its proponents believe that it is, on one level, simpler than the standard model of particle physics, against which it competes. The standard model simply states that there are various flavours of fundamental particle, seventeen or more, each with a set of properties, such as mass and charge, with no further explanation of where those come from, or why they appear in families with similar properties, or whey each particle has a given mass, charge, etc.

String theory arises as an attempt to predict the properties of these particles by considering them as modes of vibration of a one string (or in some theories surface). The usual analogy is that we once believed that the vast variety of atoms was "all there was", and the the atom was indivisible. However the patterns we see in the periodic table led us to search for a theory with fewer fundamental particles, even though such a theory was in more complicated than the original hypothesis.

It seems unlikely that string theory will make a testable prediction in the next few years, and until then the jury will be out on its validity, however I think it is a valid attempt to make sense of the zoo of particles the standard model predicts.

Isn't this just because the number of attacks (sample size) is so small it would be hard to obtain statistical significance even if the attack rate were reduced to zero?