I suspect she died a few hours ago, and they will release the news when they feel it is appropriate
I understand where you are coming from, but perhaps it is different when the actual monarch dies?
Charles will become King immediately his mother dies, and I would have thought it had to be announced then?
As a personal observation, I think that if the very last image we have of our great Queen, it is so appropriate, shaking the hand of her new, 15th! Prime Minister on Tuesday.
Looking tiny, frail, elderly, but with her radiant smile, her walking stick and her trusty handbag.
God bless our gracious Queen!
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