no longer referred to because the IET and others are now trying to cover up the mistakes they have made.
In my opinion they were not mistakes but a clumsy attempt to rationalise the situation that has developed over the years.
A compromise between [1] "earthing" to provide an adequate route for fault currents such that they are large enough to ensure dis-connect devices will operate and [2] "bonding" to ensure that in the event of a fault all metal parts that can be touched by a person will be at the same potential, the equipotential bonding.
It was complicated because the "earth" conductor in a TT system with voltage operate circuit breaker has to be insulated from earth otherwise the circuit breaker's operating coil was effectively bypassed and could not work when needed.
The guidelines are still compromised in that the equipotential bonding is almost always connected to the earth CPC in things like boilers and immersion heaters, ( electrical supply CPC to pipe work, then pipe work to equipotential bonding around the building ).
The situation is then complicated by the fact that in all but TT supplies the CPC is not connected to earth but to the neutral of the incoming supply. Which unless there is a ground rod for the neutral right at the point it enters the property will never be true earth ( ground ) potential when there is any current flowing in the neutral. ( voltage drop along the neutral ) If the only "bond" of the neutral to ground is at the substation then the potential of the "earthed" CPC in the building can be several volts different to true ground. That is not a problem inside the building as equipotential bonding keeps every at the same potential even though it is not necessarily true ground potential.
The problems come when that CPC is exported to outside the building. Gas meters and external water taps supplied by copper pipe are at the potential of the CPC and therefor may be several volts different from true ground. In a network fault condition they could be 230 volts above true ground while the buildin appears to be wth out any power. ( such as a failed neutral ). Everything in the building that is earthed or equipotentially bonded will be at the potential of the live conductor. In many situations the RCDs in the building are likely to operate but any circuit that is not RCD protected and has equipment switch on will provide a circuit through the equipment for live potential to reach the neutral and hence CPC conductors. The equipment will not work so appears to be without power and safe.
Given that set of conflicting requirements about earthing, equipotential bonding and CPC's derived from the Neutral of the supply is it any wonder the "regulations" and guidelines are at best a compromise and at worst a flawed attempt to minimise risks ?