I'm not really sure where I stand on this particular action. I think the random searches aren't that intrusive. It's one thing to randomly search someone on the street. It's another to use a facility. Public transportation IS a facility.
The question is, if they find pot - will they let it go? If they're looking for bombs, the search oughta be limited to bombs I think. I'm uncomfortable with them using a random search for any other reason.
We live in a free society and that entails an element of risk. Why you don't see the panic in London that you see elsewhere is that this is a risk that they have lived with for decades. If you'd ever been on the Underground - you would have noticed that there were no trashcans. Because they adapted from IRA bombs. They've accepted the fact that if someone wants to kill them, they're probably going to get hit in some way or fashion.
They might do all they can to prevent them, but they won't sacrifice their own rights to make sure that it doesn't happen. The same can be said of the Germans, French and Spanish. And its a lesson we should probably learn too.