The Queen's 90-year-old husband Prince Philip had a good night after being rushed to hospital for heart surgery and will be visited by members of the royal family on Saturday, Buckingham Palace said.
Britain's longest-serving royal consort, known for his outspoken and sometimes brusque manner, needed an operation to fit a small tube to clear a blocked artery after suffering chest pains as the royal family prepared to celebrate Christmas.
The Duke of Edinburgh had a good night, a spokeswoman for Buckingham Palace said. There is an expectation that some of the royal family will visit this morning.
Philip had been due to spend Christmas with members of the royal family - including Prince William and his wife Catherine, accordingly to media - at the Sandringham estate, but he may have to spend the holiday in a hospital bed.
Philip, who married Elizabeth in 1947, was taken to Papworth Hospital, one of Britain's main heart and chest centres, about 60 miles (100 km) away in Cambridge on Friday.
The Duke of Edinburgh was found to have a blocked coronary artery which caused his chest pains, the palace said. This was treated successfully by the minimally invasive procedure of coronary stenting.
He would stay in hospital for a short period under observation, it added.
The hospital declined to comment although, with members of the royal family visiting him on Saturday, it appeared unlikely he would be discharged until at least Christmas Day.
Philip had attended a lunch for staff a week ago and had been on very good form, the BBC reported.
He has had these chest pains before and I don't think it's anything untoward, but given his age they are being safe rather than sorry, former royal press spokesman Dickie Arbiter said.
Despite his age, Philip generally has been in good health and has continued a busy round of charity work and social engagements, recently visiting Australia and Ireland.
A pivotal figure in the House of Windsor, Philip has a reputation as a fiercely loyal consort who prefers outdoor pursuits to introspection.
Tabloid newspapers have delighted over the years in recounting his many public gaffes.
He once told British students in China: If you stay here much longer, you'll be slitty-eyed.
Born on the Greek island of Corfu in 1921, Philip served in the Royal Navy before marrying Elizabeth. They have four children, including the heir to the throne, Charles.
(Reporting by Matt Falloon and Peter Griffiths; Editing by Alison Williams)