Well, I guess that if a person starts shouting and swearing at no-one in particular before following a pleasant old man who has mildly rebuked him for cursing in front of women and children and then stabs him to death with a kitchen knife in front of the bus and all of its terrified passengers, then you could safely assume that he is crazy.

This actually happened a couple of years ago on Vauxhall Bridge Road in central London. I was stuck in the traffic tailback that built up as a result of the police cordoning off the area (bus included) which is a main thoroughfare from North to South London. The crime appeared on Tv's Crimewatch some months later.

I'm afraid I don't know if the arsehole was caught as I left the UK for most of '99 but if anybody knows then i'd be interested to find out.