The Duke of Edinburgh is expected to remain in hospital today, where he is recuperating following treatment for a blocked coronary artery.
Philip, 90, was spending a second night at Papworth Hospital near Huntingdon, Cambridgeshire, having undergone the coronary stent procedure.
Buckingham Palace said Philip had a "good night" following Friday's surgery and was "eager to leave".
He is expected to remain under observation for a short period but no further details have been given about when he will be discharged.
It is thought to be the first time the Duke will miss the Christmas morning service at Sandringham, the Queen's private Norfolk estate, which has become an annual tradition for the Royal Family since the early 1990s.
A large media presence is expected at Sandringham today when the Queen and her family make the short journey to St Mary Magdalene Church on the royal estate, where they are spending Christmas.
Buckingham Palace has said the service will go ahead as planned and no changes to the family's celebrations are expected.
The royals will wake to find stockings filled with small gifts and fruit at the foot of their beds.
Back at the house after the church service, lunch is served at 1pm and the family enjoys a giant turkey, reared at Sandringham.
One of the highlights of the day is undoubtedly when the royals gather around a television to watch the monarch's traditional Christmas broadcast.
This year, the monarch talks about the importance of family in the message which was recorded on December 9, two weeks before her husband was taken ill.
The Queen leaves the room and lets her family watches the national address without her.
The festive weekend will also see the Duchess of Cambridge spending her first Christmas as a member of the Royal Family.
Philip was said to be in "good spirits" yesterday as he was visited in hospital by family members, including the Queen and the Prince of Wales.
The Earl of Wessex, the Princess Royal, the Duke of York and the Duchess of Cornwall also visited the Duke's bedside.
The Queen was flown to Papworth yesterday from Sandringham.
The royal helicopter touched down near the hospital and the visitors were driven in a convoy of two Range Rovers and a third car.
The royal party returned to the helicopter after the 45-minute visit and was flown away shortly before midday, although the Prince of Wales and Duchess of Cornwall travelled separately.
Philip was taken to the specialist heart hospital on Friday night after complaining of chest pains, and, following tests, a blocked artery was discovered by doctors.
He underwent a "minimally invasive procedure of coronary stenting", which was declared a success.
Papworth describes itself as the UK's largest specialist cardiothoracic hospital and the country's main heart and lung transplant centre and carries out 2,500 stent procedures a year.
Dr Simon Davies, consultant intervention cardiologist at the Royal Brompton Hospital in London, said Philip may have been on the verge of a heart attack or could actually have suffered one before the stenting procedure was performed.
Dr Davies said: "What they have done is they put a miniature sausage-shaped balloon down the artery, pushed the balloon into the narrowed section and then blown it up.
"That forces the material that is blocking the artery outwards and then gets the blood flowing down the artery again.
"The stent is like a little metal sleeve fitted over the balloon when it is blown up.
"This metallic sleeve is opened up and then when the balloon is deflated and withdrawn the stent stays behind."
This is the most serious health scare suffered by the Duke, who is known for being a robust and active 90-year-old.
Although it is not known how long he will be in hospital, medical experts have said that many patients can be discharged a day after undergoing the procedure, providing there are no complications.
If he makes good progress he could be back among the Royal Family for the Boxing Day shoot, which he was reportedly supposed to be leading.
The Bishop of Ely, the Rt Revd Stephen Conway, began his address at the Midnight Mass at Ely Cathedral today by sending prayers and good wishes to the Queen and the Duke.
He told the congregation: "Our first thought tonight is for Prince Philip, in hospital in the diocese. We pray for him and for Her Majesty the Queen and the whole Royal Family."
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