As an obvious trusted person and favourite of the late Queen Elizabeth II, and recognized as such by her son and successor the King, he is surely uniquely qualified to assist in at least the “initial sorting” given his proximity and insight into the private personality of Her late Majesty and consideration of her wishes. It states nothing about destroying, keeping, or editing, etc, any material… just that he is part of the process. The context and clarification be might be able to provide or memories brought back are invaluable for anything we may see at some point.
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