The Duke of York - Prince Andrew - is on his way to Balmoral. The Count and Countess of Wessex, Edward and Sophie, are also travelling there, and Princess Anne is already in Scotland where she had been undertaking engagements.

All the Queen's children are either at or travelling to Balmoral, says our Royal Correspondent Jonny Dymond.

Chris Mason
Political editor

You could see the faces of concern within the House of Commons, whilst MPs listened to the statements on energy prices and bills' help from the prime minister.

There were notes being handed around, the prime minister was briefed, as were the leader of the opposition and the speaker - and people shortly after that left the chamber.

You could tell from the tenor and tone and facial expressions the concern that there is here in Westminster about the Queen’s health.

It's been a busy week for the monarch with that handover of power, her playing that crucial constitutional role in the resignation of one prime minister and the assumption of office of another.

And we've also known in terms of her interactions with political leaders that they have dialled down a little bit, certainly in terms of the physical exertions required of her to perform them have dialled down in recent months.

The overriding impression here at Westminster this lunch time is the same it will be around the country - one of deep concern from our political leaders and politicians more broadly.

Jonny Dymond
BBC royal correspondent, speaking on Radio 4

There is a degree of seriousness that we have not seen before, the very fact that the statement was issued when the palace is so reticent about making any commentary on the Queen's health.

The phrasing of the statement, that the Queen’s doctors are concerned about her health and she remains under medical supervision, and the movement of the most senior members of the Royal Family towards Balmoral, towards the Queen, all of those indicate a clear degree of concern for the health of the 96-year-old Queen.

We're not going to get great clarity from the palace, because they do not reveal the details of the health of senior members of the Royal Family.

But the fact that the family is gathering at Balmoral is an indication of the seriousness of the situation.

The Queen is under medical supervision after doctors became concerned for her health this morning, Buckingham Palace says.

In a statement, the Palace says the Queen "remains comfortable" at Balmoral.

Here's the statement in full:

The Archbishop of Canterbury has said the "prayers of the nation" are with the Queen.

Sean Coughlan
Royal correspondent

There are clearly pressing concerns for the Queen’s health– much more explicitly put than before and without any reference to this only being about difficulties with mobility.

Her close family have been informed. Prince Charles and Camilla have travelled to Balmoral and Prince William is on his way.

But there are assurances that the 96-year-old monarch is “comfortable” and remains at home in Balmoral.

There are also warnings against unfounded speculation, such as that she might have had a fall. On Tuesday she was on her feet and photographed smiling as she appointed the new prime minister.

But from last night’s last-minute cancellation of what would only have been a virtual meeting of the privy council, there is no mistaking the fragility of the Queen’s health.

Statements from the palace on the Queen's health are unusual, according to royal author Robert Hardman.

He tells the BBC: "The palace don’t normally issue bulletins on the Queen’s health, unless it's significant."

"The last time a statement as it were came out of the blue was to let us know earlier this year that she’d been diagnosed with Covid," he says.

"But on the whole, the view is if she’s not undergoing some sort of hospital medical procedure then these are private matters... so clearly the fact the Palace has seen fit to put out a statement is grounds for concern."

He adds: "Echoing the words of the [House of Commons] Speaker, I think all our thoughts will be with her at this time."

Speaker Sir Lindsay Hoyle interrupted the speech of SNP Westminster leader Ian Blackford during the energy debate in the Commons to tell MPs about the Queen's health.

The latest concerns over the Queen's health come after the postponed online meeting of the Privy Council, which was scheduled for yesterday evening.

The monarch had been advised to rest by doctors after "a full day" on Tuesday.

The Privy Council is a formal body, mainly made up of senior politicians, which advises the Queen.

During the meeting new PM Liz Truss would have taken her oath as First Lord of the Treasury and her new cabinet ministers would have been sworn into their roles.

On Tuesday, in a break with tradition the Queen met outgoing Prime Minister Boris Johnson and his successor Liz Truss in Balmoral, in Aberdeenshire rather than in London.

The Queen has suffered from mobility issues in recent times.

The first ministers of Scotland and Wales have joined the voices expressing concern for the health of the Queen.

The leader of the Liberal Democrats, Sir Ed Davey, says he is praying for the full recovery of the queen.

He says the whole nation's thoughts are with the 96-year-old monarch and the Royal Family.

In the House of Commons, Speaker Lindsay Hoyle interruped a debate on energy to send the Queen and Royal Family his "best wishes" on behalf of his fellow MPs.

"She and her family are in our thoughts and prayers at this moment," he added.

Leader of the opposition Sir Keir Starmer has also sent his thoughts to the Queen and Royal Family.

The Prince of Wales and the Duchess of Cornwall have travelled to Balmoral Castle, where the Queen is under medical supervision, Clarence House has said.

The Duke of Cambridge is travelling to Balmoral, Kensington Palace has said.

UK PM Liz Truss has just tweeted , externala message, saying her thoughts are with the monarch and her family.

She says the whole country will be "deeply concerned by the news" from the palace.

Welcome to our live coverage after Buckingham Statement released a statement saying the Queen was under medical supervision.

Her Majesty’s doctors are concerned for her health after evaluation this morning, the palace says.

She remains comfortable and is at Balmoral Castle, the statement adds.

Stay with us for live updates - and you can read our breaking news story here.