Britain's Prince Philip, the 98-year-old husband of Queen Elizabeth, was taken to a hospital Friday as a precaution for treatment of an existing condition, Buckingham Palace said.
Philip, whose official title is the Duke of Edinburgh, traveled from the royal family's Sandringham home in Norfolk, eastern England, to King Edward VII Hospital in London for observation and treatment, the palace said in a statement.
"The admission is a precautionary measure, on the advice of His Royal Highness' Doctor," it said.
A royal source said it was not an emergency admission and that the prince was able to walk into the hospital. He was expected to stay there for a few days.
Philip, who has been at his wife's side throughout her record-breaking 67 years on the throne, retired from public life in August 2017, although he has occasionally appeared at official engagements since.
He has not been seen in public since the wedding of Elizabeth's first cousin once removed, Gabriella Windsor, in May at Windsor Castle, local media reported.
Queen's schedule unaffected
The 93-year-old queen carried out the official opening of Parliament on Thursday and Philip's illness did not disrupt her plans as she was pictured arriving in Norfolk on Friday before heading to Sandringham, where the royal family traditionally gathers for Christmas.
Philip, outspoken, irascible and intensely private, and with a reputation for brusque comments and occasional gaffes, has needed hospital treatment several times in recent years.
In 2011, he spent Christmas in a hospital after an operation to clear a blocked artery in his heart, and he missed the end of celebrations to mark his wife's 60th year on the throne in 2012 after being hospitalized with a bladder infection.
The Greek-born former naval officer then underwent "an exploratory operation following abdominal investigations" in 2013.
He was admitted to a hospital in 2017 for treatment for an infection, also arising from a pre-existing condition, and last year he had hip replacement surgery that required a 10-day stay.
In January this year, he escaped unhurt when his Land Rover flipped over after a collision with another car near the Sandringham estate. He then had to give up his driving license after police gave him a warning for driving without wearing a seat belt two days later.
Elizabeth has described Philip, whom she married at London's Westminster Abbey in 1947, as her "strength and stay" during her long reign. The couple, whose relationship has been dramatized in the popular Netflix TV program The Crown, celebrated their 72nd wedding anniversary in November.