Buckingham Palace says Queen Elizabeth's husband, Prince Philip, has been admitted to the hospital for a previously scheduled hip surgery.
The Duke of Edinburgh, 96, will undergo the planned operation at King Edward VII Hospital on Wednesday.
Before resigning his position as Colonel of the Grenadier Guards at the end of previous year, Prince Philip officially retired from his public life earlier in 2017. It said the hospital admission and surgery were planned.
The Queen had marked Easter Sunday without Prince Philip at this years' service.
Officials declined to provide additional details about the surgery and said "further updates will be issued when appropriate". "That's more important than someone's chronological age".
Both the queen, 91, and Philip have suffered some health issues in recent years.
The duke was not at last Thursday's Royal Maundy Service at Leicester Cathedral, with his absence said to be because of a hip problem. He was also hospitalized for an "infection stemming from a pre-existing condition" in June of a year ago.
According to Buckingham Palace, that two-day stint in the hospital was the result of an infection related to an unnamed "pre-existing condition".
Even into his 90s, his remarks have gotten him into trouble, such as when he exasperatedly swore at a photographer at an event in 2015, ordering him to get a move on with an expletive. Philip has British and German blood through his mother, a great grand-daughter of Queen Victoria.