Random stop and searches are actually illegal (because it's a human rights issue) - but police have been performing them anyway. For it to be legal, Police need to have reasonable expectation that they will find drugs/knives etc, and need to tell you why they are stopping you.
But go ahead and give up your rights in the name of "safety".
I'm all for stop and searching. I want the police to be able to do their job without fear of being called racists by fools who have nothing better to do with their lives.