James.
The introduction of the requirement to RCD protect socket-outlets was not brought in as a whim, it was originally to protect persons using portable equipment outdoors.
At the time, there had been a noticable increase to the number of injuries and fatalities due to the increased use of the new fangled electric mowers and hedge trimmers.
The original requirement was that all socket-outlets that may reasonably be used to supply portable equipment outdoors must have RCD protection.
Since that requirement was introduced, it has been found that many designers, inspectors and electrical installers have been over-zealous in applying this requirement, to such an extent that they include socket-outlets that would not reasonably be expected to be used to supply portable equipment outdoors. Such as those used to supply integrated appliances etc.
It was decided with the introduction of the 17th edition, to clarify the requiremnts to RCD protect socket-outlets, and to not only require that those used to supply portable equipment outdoors, but to include portable equipment used by unskilled persons indoors as well.
To this end two requirements were introduced, one requiring any socket-outlet intended for general use by ordinary persons to be RCD protected, and the other requiring specifically any socket-outlet that is used for mobile equipment outdoors should also be RCD protected.
As such, if you have a socket-outlet that could be used to supply mobile equipment outdoors, but you don't use it for that purpose, there is no requirement for it to be RCD protected.
However if that socket-outlet is used for a hoover, for charging laptops or any of the other myriad of new fangled items we now have, it must also have RCD protection.
Socket-outlets intended for specific use, such as to supply integrated appliances, boilers etc. do not require RCD protection, as it is unlikely that someone will be lugging such applances around and the likely hood of someone recieving a shock is slim.
It has also been determined that ordinary persons are quite thick, and will now indulge in DIY (especially when there is a bank holiday).
These people will insist on drilling and nailing where any reasonable person would not.
So the requirement to additionally protect cables concealed in walls has been extended to include RCD protection.
For some reason (which is a mystery to me) it has been decided to allow these people to have socket-outlets in their bathrooms.
I have seen an installation, where a 42" flat screen TV was installed into a stud wall of a bathroom. The TV was sealed off from the bathroom by some acrylic plastic, and the socket-outlet was outside the bathroom. Apparently it is possible now to obtain a TV that can be tiled into a bathroom or shower, and that when it is not on, doubles up as a mirror.
So you can now watch TV whilst showering, then quickly squeeze your pimples during the commercial breaks.
As such these socket-outlets also require RCD protection, along with them being 3.6m from the bath or shower. Perhaps it has been decided that these people will not have long extension leads.
It was decided that sensible or skilled persons would not be too thick to just start putting pictures, shelving and flat screen TVs up willy nilly without first determining whether there were concealed cables in the way, and that they would not use mobile equipment indoors with damaged cables. So exceptions were made for these persons to the requirements for RCD protection. Not that sensible that any exceptions for RCD protection in bathrooms or for mobile equipment used outdoors to be allowed.
Obviously, the easiest way to protect the socket-outlets that do need RCD protection, and at the same time cables concealed in walls, is to protect the whole circuit.
However to accomodate such installations where cables are not concealed in walls, where other aditional protection is used and where some socket-outlets are required whithout RCD protection, RCD protection for circuits other than in special locations is not required.
