A spokesperson for the Duke and Duchess of Sussex confirmed that Prince Harry was heading to Scotland, where the Queen is receiving medical care at Balmoral Castle.
Queen Elizabeth's grandson, 37 was scheduled to attend the WellChild Awards in London on Thursday. He travelled from their California home to Europe this week for a series of visits with their longstanding charitable organizations.
Buckingham Palace said in a statement Thursday morning,
"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."
Prince Harry joined family members in rushing to Queen Elizabeth's side.
The Queen's son and heir, Prince Charles, and his wife, Camilla, Duchess of Cornwall, have travelled to Balmoral. Prince Charles was in Scotland on Wednesday carrying out engagements.
Prince William, Harry's brother who is second in line to the throne, is also heading to Scotland. He was seen in photos Wednesday as he joined Kate Middleton in bringing their three children to a preview day at their new school.
Queen Elizabeth's other three children are also making their way to Balmoral. Princess Anne, the Queen's only daughter, is already in Scotland having undertaken royal duties in the country this week. Prince Andrew and Prince Edward, along with his wife Sophie, Countess of Wessex, are also going to see their mother.
Queen Elizabeth was last seen in photos on Tuesday, where she appointed Conservative Party leader Liz Truss as the U.K.'s new prime minister at Balmoral.
Truss tweeted in reaction to the palace's statement on Thursday, "The whole country will be deeply concerned by the news from Buckingham Palace this lunchtime. My thoughts—and the thoughts of people across our United Kingdom—are with Her Majesty The Queen and her family at this time."