Problem is that the people that are supposed to throw that book are just as morally (but potentially not only morally) corrupt and may too have skeletons in their closet. It is a systemic problem. The Post Office wouldn't have taken such a gamble unless they knew they'd be able to talk their way out of any consequences should it backfire.
Retired, wealthy, and had lost all her various posts at NHS, church etc. AFAICT.
Indeed. But who are they who lied to the courts? This article says the BBC has a false Statement of Truth signed by one of them, but does not name them.
Sadly in this country the establishment has a history of protecting those of a certain status in society. Even if there is a prosecution, it will likely be dragged out for so long that those culpable will die before a sentence is passed.