Prince Harry is in the UK and is making his way to Balmoral to be with the rest of the Royal Family amid news of the Queen's ill health.
He and his wife Meghan Markle 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 - in London this evening.
Harry was expected to make a speech at the ceremony this evening, but now he is on his way to see his grandmother.
Meghan had originally planned to travel with Harry to Scotland but she will now remain in London, but will not attend the awards.
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.
Buckingham Palace released a rare statement on the Queen's health this afternoon as her senior royals rushed to be with her at Balmoral.
In a statement, the Royal spokesman said: "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 remains comfortable and at Balmoral."
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.
Harry was due to give a speech at the WellChild Awards on Thursday evening and celebrate the achievements and resilience of seriously ill youngsters and their families.
The duke has been patron of WellChild, the national charity for seriously ill children and their families, since 2007 and despite stepping down as a working royal has maintained his links with the organisation.
Harry and Meghan, who have been visiting Europe this week, attended the One Young World summit in Manchester on Monday.
Meghan delivered a keynote speech and declared it was "very nice to be back in the UK" and told the young leaders "you are the future, you are the present".
It was their first public appearance in the UK since they joined other members of the royal family for events in June that celebrated the Queen's Platinum Jubilee.
They also travelled to Dusseldorf in Germany on Tuesday, to mark the one-year countdown to The Invictus Games in the city, and thrilled fans when they went on a walkabout.
