I was just reminiscing with a friend and we are not really sure it does anymore. She was raised in Leatherhead where you can apparently still leave your front door open during the day (if you want to!) without anything happening.
It needs to tick these boxes:
Little/no antisocial behaviour and low crime rate. Safe for teenagers to walk home in the dark
Excellent nearby hospital with high staff retention/satisfaction
Lot of green spaces and community centres
Some form of transport link into c. London (even if it is a couple of buses per day)
Affluent population (I know - but I am looking for an ideal!)