This was a straightforward replacement to allow a new circuit to be added to the existing installation and to provide RCD protection to all electrical circuits in the house.
These pictures are reproduced with kind permission from "Mr & Mrs R" from Donnington.
This second installation was to replace a 25 year old RCD with a replacement so that when a circuit tripped all circuits would not fail. This was particularly annoying as the electric garage door was disabled (and the RCD is in the garage!!!).
A modern unit was installed and all circuits tested and a few ring main circuit problems that were found were fixed.
This picture was reproduced with the kind permission from Mr B of Wellington.