There appears to be a common misconception, that a skilled person has to be a qualified electrician.
This is not so.
All a skilled person has to have, is knowledge that there is a risk of electrocution or fire when using electrical equipment, and how to avoid those risks.
Such knowledge could be to check for damage and to not use the equipment if any damage is evident.
There are two Statutory documents which relate to workers and dangers in the work place.
One is the HSWA 1974 and the other is EAWR 1989.
Regulation 2(c) of the HSWA requires an employer to ensure: "the provision of such information, instruction, training and supervision as is necessary to ensure, so far as is reasonably practicable, the health and safety at work of his employees;".
Regulation 16 of the EAWR requires: "No person shall be engaged in any work activity where technical knowledge or experience is necessary to prevent danger or, where appropriate, injury, unless he possesses such knowledge or experience, or is under such degree of supervision as may be appropriate having regard to the nature of the work."
These two Statutory requirements make it a legal requirement that any worker or employee meet the requirements to be considered either a 'skilled' or 'instructed' person as defined by BS7671 when carrying out work related duties where electricity may present a danger.
If an employer were to allow an employee who doesn't meet the requirements of BS7671 to be considered a 'skilled' or 'instructed' person, to carry out a work related duty where electricity could present a danger, that employer would be breaking the law.
BS7671 does not provide Regulations or requirements for instances where people would act illegally.
It's considered that if someone is prepared to act illegally, then it is very unlikely that they will at the same time comply with any non-statutory Regulations or requirements.
The requirements for RCD protection apply in the main to domestic installations, because there are no statutory requirements relating to the type of person who would use such an installation.
The first part of the requirement for RCD protection relating to socket-outlets, indicates that the requirement only relates to where the socket-outlets are used by ordinary persons.
The second part indicates that the requirement relates only to those socket-outlets that are intended for general use.
As such the requirement to provide RCD protection for socket-outlets only relates to those socket-outlets that are intended for general use by ordinary persons.
Socket-outlets that are intended for connecting washing machines, fridges, dishwashers, microwaves, cookers, boilers even TVs are not required to be provided with RCD protection.
There are two exceptions to the requirement, and to be honest the exceptions are redundant.
One is for where the use of a socket-outlet by an ordinary person is supervised by a skilled or instructed person.
If the ordinary person is being so supervised, then they are effectivly being instructed and would no longer be considered as an ordinary person.
The other is for where a general use socket-outlet is specifically labeled or otherwise identified as being for use to connect a specific item of equipment.
If a socket-outlet was intended for use only to connect a specific item of equipment, then it would not be considered as being intended for general use, and the exception would not apply.