The big news anchors called in early and wearing black suits and TV schedules suspended until 6pm, road signage removed from the front gate at Balmoral and fences put up, parliament suspended, the whole Royal family travelling to Scotland…
plus a BBC journalist accidentally announcing it at 3pm on Twitter and then giving the most cagily worded retraction I’ve ever read: “I tweeted that there had been an announcement about the death of the Queen. This was incorrect, there has been no announcement, and so I have deleted the tweet. I apologise.”
Personally, I was pretty sure she was gone two to three hours before the formal announcement. Plenty of time to do quite a lot of Wikipedia updates and just click “Save” when the announcement finally breaks.