The BBC's Royal editor Nicholas Witchell has explained why Buckingham Palace's recent 29-word statement on the Queen's health is so immensely important.
Earlier today, Buckingham Palace confirmed concerns have been raised about the Queen's health in a statement.
The concerning statement from Buckingham Palace read: "Following further evaluation this morning The Queen’s doctors are concerned for Her Majesty’s health and have recommended she remain under medical supervision.
"The Queen is comfortable and at remains at Balmoral."
Following the statement, news broke that Queen Elizabeth's immediate family members have all dropped their prior engagements to come together and be with the monarch amid huge concerns for the 96-year-old's health.
The BBC are also now running a special news programme up until 6pm on to provide updates on the Queen's condition.
Sharing his thoughts on the concerning statement from Buckingham Palace, BBC's Royal editor Nicholas Witchell said it's a 'very significant moment' in the history of the UK.
"I think this is clearly a very significant moment. For all of the reasons that we have been saying over the last hour or so," he said.
"The fact that the palace, which doesn’t usually comment on the state of her health or the progression of her wellbeing.
"The fact that it is saying that the doctors are concerned, though they say she remains comfortable at Balmoral.
"The fact that immediate family members are gathering at Balmoral.
"Prince Charles who is of course staying at the Balmoral estate at Birkhall, he’s traveling over and has been regularly going to see his mother while he’s been staying there.
"The fact that I think says the most is the fact that Prince William is flying up to Balmoral from the south. So I think, all in all, this is a very sombre moment."
It comes as Prince Harry and wife Meghan are in the UK and are on their way to Balmoral to be with the rest of the Royal Family amid news of the Queen's ill health.
The couple were due to attend the WellChild Awards - which celebrates the inspirational qualities of the country's seriously ill children and those who go that extra mile to make a difference to their lives.
Harry was expected to make a speech at the ceremony this evening, but not he and Meghan will make their way to Scotland. The Duke and Duchess of Sussex were on the last leg of their UK tour and have not yet seen the Queen or any of the royals.
Princess Anne has already arrived at the Scottish estate with Princes Edward and Andrew believed to be en route.
The nation's longest-reigning monarch has ongoing mobility issues and looked bright but frail and used a walking stick during Tuesday's historic audience with Ms Truss, which followed a visit from outgoing prime minister Boris Johnson as he tendered his resignation.
