[Jon]

Sky News have answered a question about presenters wearing black prior to the announcement in their Q&A this afternoon:
news.sky.com 

It's customary for on-air reporters and presenters to wear black as a mark of respect in the event of the death of a senior member of the Royal Family. 

Last Thursday afternoon, it was clear that the Queen was gravely ill and our broadcasters were dressed appropriately to report the anticipated announcement of her death from Buckingham Palace. 

It's nothing we don't know already, but it's interesting that they're addressing it. When looking back at the coverage, I can understand why people have been saying "they knew for hours" even if that wasn't really the case.

It’s also should be pointed out that there was literally no turn around time from the point the Queen was officially still alive to having had passed away. So unless the likes of Huw Edwards were going to quickly change their tie out of vision there was no way around it for broadcasters. So from their point of view it turned out to be right call. It was just enough in a long line of clues from the palace and indeed the broadcasters something was going to happen.