I've just started reading Rivers of London and the opening page has this little gem...
"... Being a seasoned Londoner, Martin gave the body the 'London once-over' - a quick glance to determine whether this was a drunk, a crazy or a human being in distress. The fact that it was entirely possible for someone to be all three simultaneously is why good-samaritism in London is considered an extreme sport - like base-jumping or crocodile-wrestling."