“…special guardianship is an issue of very great importance to everyone concerned with it, not least, of course, the child who is its subject. It is plainly not something to be embarked upon lightly or capriciously, not least because the status it gives the special guardian effectively prevents the exercise of parental responsibility on the part of the child's natural parents, and terminates the parental authority given to a local authority under a care order (whether interim or final). In this respect, it is substantially different from a residence order which, whilst it also brings a previously subsisting care order in relation to the same child to an end, does not confer on any person who holds the order the exclusivity in the exercise of parental responsibility which accompanies a special guardianship order.”