The Royal Family spent part of Christmas Eve day at the bedside of Prince Philip, who is in hospital with a heart ailment.
Doctors said the Queen Elizabeth's 90-year-old husband could have suffered a heart attack Friday but they couldn't say for certain without further information.
The prince was taken to Papworth Hospital in Cambridge late Friday after complaining of chest pains. He and other royals had been at the Queen's Sandringham estate in nearby Norfolk preparing to celebrate Christmas.
Doctors inserted a coronary stent to clear a blocked artery but could not say more about the prince's condition. A Buckingham Palace spokesperson said he is currently "under observation" and will have "a short stay" in hospital.
The Queen and three of her children, Princess Anne and Princes Edward and Andrew, were flown to the hospital by helicopter around 11 a.m. Saturday for a 45-minute visit.
They were then flown back to Sandringham.
An hour after the Queen arrived, Prince Charles and his wife Camilla paid a visit to his father.
Prince Philip "is in good spirits but he is eager to leave" hospital, a palace spokesperson said.
British Prime Minister David Cameron sent his best wishes to Prince Philip.
"The prime minister has been kept informed of the situation and wishes the Duke of Edinburgh a very speedy recovery," Cameron's office said.
Even with her husband in hospital, the Queen plans to attend church as usual on Christmas morning and to deliver her annual Christmas address to the Commonwealth.
With files from The Associated Press
