Lucy Manning
Reporting from Buckingham Palace

Image source, Reuters

At Buckingham Palace some tourists are in tears at the news about the Queen's health.

Sue and Andy Alderman from Somerset were visiting London and decided to head to Buckingham Palace when they heard the announcement that the Queen was unwell.

They said they were stunned by the news but that they thought the Queen had been looking frail since the death of the Duke of Edinburgh. They hoped there would be better news about her health.

Pam Fleming and Kim Tierney from Australia were on a tour of the building when they heard the news.

Pam told me crying that: "She's the only Queen we've had. All of my life. She's such a lovely lady. It's such a shock." They added they were both thinking of the Queen's family at this time.

As would be expected, journalists, photographers and camera crews from across the world are now reporting from outside Buckingham Palace, where just months ago the Queen appeared waving from its balcony during her Platinum Jubilee celebrations.

A flight carrying seven members of the Royal Household is expected to land at Aberdeen Airport shortly, the BBC understands.

The plane is travelling from RAF Northolt in London.

It’s not known exactly which members of the household are on board.

Nicholas Witchell
BBC royal correspondent

Prince Charles is at Balmoral. He will be at his mother's side.

He is the oldest and longest serving heir apparent in British history.

We've seen him standing in, deputising for her, in recent months.

Image source, Reuters

Balmoral Castle has long been one of the Queen's favourite places and she is said to never be happier than when staying there.

Today, outside the gates of Balmoral, there is a sombre atmosphere. Some cars have been seen driving in through its gates in the last hour.

Image source, .

Nicholas Witchell
BBC royal correspondent

I understand Buckingham Palace is not expected to say anything more at this stage. There is nothing imminent I am led to believe.

Sean Coughlan
Royal correspondent

Prince Harry and Meghan, the Duke and Duchess of Sussex, are on their way to Balmoral, where the prince’s brother William is already headed.

It will mean the Sussexes pulling out of a charity event in London where they had been the chief guests – and their already high-profile visit to the UK has clearly been overtaken by events.

The couple have also been in Germany for an event to do with the Invictus Games in a year's time.

After a week of headlines about family tensions, and a lack of family gatherings, they will be meeting again in a way that had not been expected.

Some more political reaction to bring you now from another former prime minister, Sir Tony Blair.

The former Labour PM writes on Twitter he is also "deeply concerned" by the news about the Queen's health.

He writes: "My thoughts and prayers are with Her Majesty the Queen and her family at this worrying time."

Nicholas Witchell
Royal correspondent

The statement from Buckingham Palace is significant because it is a contrast to the last couple of months, when Buckingham Palace said as little as possible.

It said she remains comfortable at Balmoral.

But the fact that Buckingham Palace felt it necessary to issue a statement, and the fact that family members are travelling there, says everything.

As the prime minister has said, the whole country will be deeply concerned and I think that we must assume that there are reasons for that.

There has been this gradual deterioration in the Queen’s health over the past months. Clearly over the past 24 to 48 hours the doctors have become rather more concerned.

Image source, Getty Images

The Queen's former press secretary Dickie Arbiter says his immediate thought is that we should be concerned but says the situation is unprecedented.

“It is a family moment, but it is also a very important moment not just for the nation but also for the Commonwealth," he tells the BBC's World at One.

"There will be concern throughout the world, in every country that has dealings with the UK or has had a visit by the Queen, she is an international figure, she’s been on the throne for 70 years - that is a long time so I think there will be global concern," he says.

“The statement is unprecedented so we haven’t been into this territory before. If there is something to say Buckingham Palace will say it - but there will not be constant updates, that’s something they do not do," he adds.

Image source, Getty Images

The traditional ceremony of the Changing of the Guard, which was due to take place outside Buckingham Palace tomorrow morning, has been called off.

A sign has been placed in an area at the front of the palace where the iconic drills take place, to let tourists know it is cancelled.

However, this sign was later removed by officials.

Cardinal Vincent Nichols, the Archbishop of Westminster and head of the Catholic Church in England and Wales, has said he’s "concerned" by the news of the Queen’s health.

He also offered his prayers, adding: "May the blessings of the Lord strengthen and comfort her and her family."

The UK's Chief Rabbi has expressed similar sentiments, saying the Queen “is very much in my prayers today”.

Ephraim Mirvis, the Chief Rabbi of the United Hebrew Congregations of the Commonwealth, said: "I know that Jewish communities around the Commonwealth will join me in wishing her a full and swift recovery."

The Muslim Council of Britain has wished the Queen a “swift and lasting recovery” and offered its prayers for the monarch and the Royal Family.

Leader of the Democratic Unionist Party in Northern Ireland, Sir Jeffrey Donaldson, has tweeted out his reaction.

Dozens of well-wishers have gathered outside the gates of Balmoral Castle in Aberdeenshire.

Police officers stand guard of the gates of the driveway leading up to the Castle where the Queen is being joined by members of her family.

Buckingham Palace said in its statement that the Queen was at the castle and was "comfortable" .

Image source, Reuters

Image source, Reuters

The careful wording of the palace statement suggests "something serious is possibly going on", says former BBC royal correspondent Richard Sumner.

Speaking on BBC News, he says: "The whole policy of the palace has always been understatement and I've always suspected that possibly there was more than a mobility problem concerned here."

Along with advancing age there may be other more complicated medical problems, he says.

"When you're 96, of course you can’t expect to have the health of a 25-year-old.

"Hopefully this is a passing storm that can be overcome but I think that judging from the careful wording of the palace something serious is possibly going on here."

Sumner adds: "People who’ve seen her say that mentally she’s sharp as a tack and very interested in everything still."

He says it seems "her body is giving out on her" – though it's not clear "quite in what way or how badly".

Image source, Getty Images

Former Conservative prime minister David Cameron has tweeted his "deep concern" at the news.

On Twitter he wrote: "I send my heartfelt thoughts and prayers to Her Majesty The Queen and the Royal Family at this worrying time."

We're hearing all the Queen’s children are either at or on the way to Balmoral.

The monarch has four children, eight grandchildren and 12 great-grandchildren:

• Prince Charles, the Prince of Wales, is her eldest child and the heir to the throne. He is married to Camilla, the Duchess of Cornwall
• Princess Anne, the Princess Royal, is the Queen's second child and only daughter. She is married to Vice Adm Timothy Laurence and has two children with her first husband, Captain Mark Phillips - Peter Phillips and Zara Tindall
• Prince Andrew, the Duke of York, is the Queen's third child and has two daughters with his former wife, the Duchess of York - Princess Beatrice and Princess Eugenie. He stepped down as a "working Royal" in 2019 after a controversial Newsnight interview
• Prince Edward, the Earl of Wessex is her youngest child. He is married to Sophie, the Countess of Wessex and they have two children - Louise and James Mountbatten-Windsor
• Prince William, the Duke of Cambridge, has also travelled to Balmoral today. The eldest son of Prince Charles and his first wife, Diana, Princess of Wales, he is married to Catherine, the Duchess of Cambridge. They have three children - Prince George, Princess Charlotte and Prince Louis

In the last few moments we've had some images of Aberdeen Airport - the nearest airport to Balmoral Castle - showing people getting off a jet and into a car.

It is not clear who it is, but we know the Queen's children are either at Balmoral with her or are on their way to Aberdeenshire.

The Duchess of Cambridge has remained in Windsor as Prince George, Princess Charlotte and Prince Louis are on their first full day at their new school, Kensington Palace has said.

Prince William and Kate's three children have all started Lambrook School, in Berkshire, after the family's recent move to Windsor from their home in nearby London.

Image source, PA Media

The Queen is said to be in a comfortable state at her royal residence in Balmoral.

Balmoral Castle is situated in Royal Deeside, Aberdeenshire, Scotland.

It has been a royal residence for over 150 years, and was first used as a holiday home by Queen Victoria and Prince Albert.

It is said to be one of the Queen's favoured residences and she has spent more time there over the last year.

Earlier this week, Liz Truss travelled to the castle to be appointed as the new PM by the Queen, because of concerns that the 96-year-old monarch might have to change plans for travel to London at short notice.