Sorry Antony. my iPad had not full refreshed I see your comment and I get your point.
Yes many years ago we just relied on a fuse and they were very good, then RCD came along. I agree there is an over reliance on them.
" we may have a problem or I'm not sure if we do or not , I know lets thrown an RCD at it"
The way I look at it the first cars didn't have seat belts, after a few accidents seat belts came along. Then a few years later we got air bags,
Things improve all the time. RCDs make installations safer.
As for the installation it's hard to tell but from an experience I had with twin and Earth sub mains they were in the stud wall of the room quite obvious the cable zone when your in the room . But this wall formed the out side corridor. At this point it was not obvious of the cable safe zone
I don't believe put a RCD on sub main on is a good idea ( that is down to the designer of the circuit) . But it would conform with the regulations. Cables buried in the fabric of the building with out RCD protection is a code on an EICR and if it's a commercial building then there are health and safety issue as well.
In my case we replace the sub mains with SWA, as the level,of disturbance which was reasonable foreseeable by installing an RCD was not acceptable to him as a business.
Either way unprotected cable buried in to the fabric of the building needs RCD protection, if you can verified these cables are buried deep enough through and run in safe zones happy days, if not then you need to think very carefully on how you coded it.
Hence if they had all there paper work I would have confidence they were on the ball and in control of their installation I may be persuaded to give them a code 3,
Personally I am not in the business of trying to give satisfactory EICR as if I'm not happy it's unsatisfactory.