Queen Elizabeth II's husband Prince Philip was set to miss the royals' traditional Christmas pheasant shoot Monday after a third night in hospital following heart surgery.
Philip, 90, was rushed to hospital on Friday complaining of chest pains and required an emergency procedure to unblock a coronary artery.
The prince, known as the Duke of Edinburgh, spent another "good night" in hospital, a Buckingham Palace spokesman said on Monday.
He was given a festive boost on Sunday with a Christmas Day visit from grandsons Prince William and Harry and four other of his eight grandchildren.
Philip, who has a famously brusque manner, is said by aides to be eager to leave the Papworth Hospital in Cambridgeshire, eastern England, but no date for his release has been given.
He usually leads the royal family's shoot at their Sandringham country estate, held on 26 December, or Boxing Day as it is known in Britain. The shoot was expected to go ahead as planned. In a statement on Sunday, the Palace said he was "in good spirits and will remain in hospital under observation for a short period.
"The Queen will continue to be briefed on his condition. We do not have details of a release date at this stage."
The queen visited her husband of 64 years at the hospital on Sunday after the royal family's Christmas church service.
Later in the day, the prince's grandchildren swept into the hospital, which lies 80 kilometres (50 miles) from Sandringham, in a fleet of cars.
Although William's wife Catherine appeared at the church service for the first time following their wedding in April, she did not come to the hospital.
William, the 29-year-old second in line to the throne, was accompanied by Zara Tindall and Peter Phillips, the children of the queen's daughter Princess Anne.
Prince Harry, William's younger brother, drove to the hospital in a separate car which also carried Beatrice and Eugenie, the daughters of the queen's second youngest son Prince Andrew.
The royals told hundreds of wellwishers who had gathered on Sunday to see them attend the Christmas service in the St Mary Magdalene church at Sandringham that Philip's condition was improving.
William said his grandfather was "very well, thank you. Getting much better", while Prince Philip's eldest child Prince Charles said his father was "very well".
Philip earlier told doctors he felt "fine" and didn't want to "make a fuss", adding: "I just want to go home," according to reports.
The Greek-born Philip is the longest serving royal consort in British history and has become a national institution -- almost as much for his often off-colour remarks as for his support for the queen.
The heart operation is his most serious health scare to date.
Despite his age, the prince remains active although he has reduced his public engagements this year.
He travelled with the 85-year-old queen to Australia in October although he pulled out of a visit to Italy just afterwards because he was nursing a cold.
The operation he underwent involves fitting a mesh sleeve fitted over a sausage-shaped balloon into the artery.
The sleeve, or stent, remains fixed in position inside the body when the balloon is removed and opens up the artery to remove the blockage.
Papworth is Britain's largest specialist cardiothoracic hospital and the country's main heart and lung transplant centre.
Next year is a big one for the queen as she celebrates her diamond jubilee to mark 60 years on the British throne.