The BBC presenters, including Huw Edwards, have all changed into black suits as they helm rolling coverage of health concerns for the Queen.
The Queen is under medical supervision at Balmoral after doctors became concerned for her health, Buckingham Palace has said.
The Queen's children and grandchildren are either at, or are travelling to, her Scottish estate near Aberdeen.
Huw Edwards is helming the coverage alongside the BBC ’s Royal Editor Nicholas Witchell, both of whom were wearing black suits and ties as they discussed the worrying situation.
“Following further evaluation this morning, the Queen's doctors are concerned for Her Majesty's health and have recommended she remain under medical supervision,” a statement said.
“The Queen remains comfortable and at Balmoral.”
The BBC has cleared its scheduled programming following the announcement, cutting short its midday show for a news special.
The broadcast was interrupted during Bargain Hunt, as a BBC newsreader confirmed: “Welcome to viewers on BBC One. We have had news from Buckingham Palace that the Queen is under medical supervision at Balmoral.”
She then detailed concern for the monarch's health, and the news remained on air instead of returning to usual programming.
While the BBC scrapped programming, other channels including ITV and Channel 4 remained with regular schedules.
A number of BBC viewers noticed the presenters were all donning black and took to Twitter to note, with one writing: “Seems like they've started putting on the black suits at the BBC, as part of the protocol.”
A second tweeted: “BBC going into rolling coverage mode and the anchor donning the black suit suggests someone has hit the proverbial big red button somewhere.”
A third wrote: “BBC just brought Huw Edwards into studio wearing a black suit and a black tie. Draw your own conclusions.”
“Over the last half-hour, all the BBC presenters, and the BSL signing guy, have all changed into black suits…” another posted.
Prince Charles has travelled to Balmoral with his wife the Duchess of Cornwall, while The Duke of York and the Count and Countess of Wessex are travelling to the Scottish estate.
The Duke of Cambridge is also on his way, as are the Duke and Duchess of Sussex, who were due to attend a charity event in London.
