Just after 12:30 this afternoon, Buckingham Palace issued a statement saying the Queen's doctors were concerned about her health, recommending she remained under medical supervision.

Soon after that, we heard news that all the Queen's children were either already with her at Balmoral Castle in Scotland or travelling to be with her.

Prince Charles, Camilla and Princess Anne are at Balmoral.

Prince William, the Queen's grandson and second in line to the throne, is on his way there, while his wife Kate, Duchess of Cambridge, has remained in Windsor as her children are on their first full day at their new school.

Prince William's brother, Prince Harry, and his wife Meghan had been in the UK in recent days for engagements, and are said to be travelling to Scotland too.

On Tuesday, newly appointed UK PM Liz Truss had herself travelled to Balmoral to be appointed by the Queen, in a break with tradition as the monarch would have normally seen her in London. But the Queen had suffered from mobility issues recently and so the meeting was moved to Balmoral.

The plane carrying seven members of the Royal Family has landed at Aberdeen airport.

It's not known who exactly is on the flight from RAF Northolt, although we know that Prince William, Prince Harry and Meghan, Prince Edward and Sophie, and Prince Andrew are all travelling to Balmoral.

Aberdeen airport is about an hour's drive from Balmoral Castle.

The plane that's landed in Aberdeen was carrying the Duke of Cambridge, the Duke of York and the Earl and Countess of Wessex, the BBC understands.

Figures were seen disembarking the plane and getting into cars on the airport runway. It's expected they will now travel to Balmoral Castle - a journey of around an hour.

The town, which is normally full of tourists, is quieter as it's been raining all afternoon.

But some of those who have ventured out to visit Windsor castle - the Queen's main residence - said they found out about the Queen's condition after overhearing castle staff talking about it.

Others found out as they left the grounds.

Some people from outside Windsor have also started travelling to this royal town.

One woman I spoke to had travelled from west London. She said after hearing the news, she wanted to be in Windsor.

Today's news reminds us of Queen's importance, says royal biographer

A little earlier we heard from royal biographer Robert Hardman, author of Queen of Our Times.

He says today's news about the Queen's health has reminded us of her importance to the country and our affection for her.

"She is unlike any other monarch in our history – she’s our longest-lived, longest-serving, longest-reigning monarch," he tells BBC 5 Live.

He adds that her sense of public duty pre-dated her accession to the throne in 1952.

"She just stands for this constancy, this sense of permanence and stability.

"And I think over the years people have probably taken her for granted often.

"Suddenly, at times like this, we all realise... how precious she is."

President Biden's thoughts are with the Queen - spokesman

In the last few moments, the White House has said US President Joe Biden's thoughts are with the Queen and her family.