Thanks that all makes sense. But in an earth fault condition, that would still become live - and would be the last connected conductive part before ground. Does that not make it potentially more dangerous to be in contact with?
Edit I appreciate that no matter what most current will still want to travel to ground, not through anyone touching it - but there is still some low level risk of making contact isn't there?
Ok, Lee has already explained this but since you are not a qualified spark I will briefly explain it to you in basic lay mans terms.
Its all about potential.
Basically what this means is that current will flow down the path of least resistance, the better the conductor the better the current will flow. So in a fault condition to prevent shock, if someone was unfortunate enough to come into contact with an exposed conductive part, we want to divert as much current from passing through that person as possible. The amount of current passing through the person depends (basically) on what the voltage is and what the resistance is between the live part, person and earth. Hence why birds can sit on high powered supply lines and not get harmed, the resistance to earth is so high (because they are not in contact with the earth) the current cannot easily flow.
Now basically what the earthing and bonding do in an electrical installation is to make all exposed & extraneous conductive parts at an equal potential and the path to earth as least resistive as possible (there is a bit more to it than that but we won't go into the details). So even during a direct fault where the current flowing through the earth conductor is high, directly touching it (depending on a few factors) will not give you a harmful shock because the current will mainly flow through the path of least resistance (the earth conductor).
In addition there are protection devices - fuses, mcbs, rcds... in place so that if a fault was to arise they are designed to cut the supply very quickly so the fault current would only pass through the earth conductor for a very brief moment. In other words its extremely unlikely that anyone would be in contact with the earth conductor, or in the case of the OP connection point, plus creating a lower resistance to earth, for the brief moment a fault current was being conducted.
All this is basically what Lee mentioned and is commonly termed as - ADS.
And for you trainees out there - all this is why it is very important that during your installs and testing that you ensure that all the earthing & bonding is present and correct. It is the most important thing to consider for an electrical installation!
Hope this explains it for you.