William and Harry visit Prince Philip in hospital
Six of Prince Philip's grandchildren, including Princes William and Harry, have visited him in hospital.
The Duke of Edinburgh, who is 90, had a coronary stent fitted at Papworth hospital in Cambridgeshire, after suffering chest pains on Friday.
Princesses Beatrice and Eugenie, Peter Phillips and Zara Tindall also visited.
Sunday night will be Prince Philip's third night in hospital. No details have been given about when he will be discharged.
A Buckingham Palace spokesman said the duke was in "good spirits" and would remain under observation, and that the Queen continued to be briefed.
The spokesman said the duke was expected to be in hospital for "a short period", but did not elaborate on what a short period was.
The Royal Family have been celebrating Christmas at Sandringham, the Queen's private Norfolk estate.
Earlier, prayers were said for the prince during the family's traditional Christmas Day church service at St Mary Magdalene Church in Sandringham.
Afterwards, the royals - including, for the first time, the Duchess of Cambridge - greeted well-wishers. The Queen attended the service, along with the Prince of Wales and Duchess of Cornwall, Prince Harry, and the Queen's granddaughter Zara Phillips with her husband Mike Tindall, whom she married earlier this year.
In her annual Christmas Day broadcast, the Queen focused on the strength of family, friends and the community working together.
She said the Royal Family had been inspired by the courage shown in Britain, the Commonwealth and around the world.
"We've seen that it's in hardship that we often find strength from our families; it's in adversity that new friendships are sometimes formed; and it's in a crisis that communities break down barriers and bind together to help one another," she said.
"Families, friends and communities often find a source of courage rising up from within.
"Indeed, sadly, it seems that it is tragedy that often draws out the most and the best from the human spirit."
The message was recorded on 9 December, before her husband was treated in hospital.
The Queen visited the duke in hospital on Christmas Eve, accompanied by their sons Edward and Andrew, and daughter, Anne.
The Prince of Wales and the Duchess of Cornwall also then visited.
The "minimally invasive" coronary stenting procedure the duke underwent involves pushing a balloon into the artery and inflating it to remove the blockage.
'In good shape'
Prince Philip was last in hospital in April 2008, when he spent three days in London with a chest infection.
Speaking ahead of his 90th birthday, in June, the duke said he wanted to slow down. He stepped down as president or patron of more than a dozen organisations.
Royal biographer Penny Junor said the duke was generally in good health for his age.
"He is an extraordinarily fit man. He takes a lot of exercise, he does an awful lot of work. He's in very good shape generally."