Prince Philip, the 96-year-old husband of Britain's Queen Elizabeth, has been admitted to hospital with an infection and will miss the formal opening of parliament, but he remains in good spirits, Buckingham Palace said.
Philip, whose official title is Duke of Edinburgh and has sometimes drawn attention with headline-grabbing gaffes, has been by the queen's side throughout her 65 years on the throne and she has described him as "my strength and stay".
"The Duke of Edinburgh was admitted to King Edward VII Hospital in London last night, as a precautionary measure, for treatment of an infection arising from a pre-existing condition," a spokesman for the Palace said.
"Prince Philip is in good spirits and is disappointed to be missing the State Opening of Parliament and Royal Ascot," the spokesman said.
The queen, the world's longest-reigning living monarch, celebrated her 91st birthday in April. She will be accompanied in parliament by her son, Prince Charles, who is heir to the throne.
When Philip announced in May that he would retire later this year from active public life, he quipped about not being able to "stand up much".
Outspoken, irascible and intensely private, Philip, a Greek-born former naval officer, has a reputation for brusque comments and occasional gaffes.
Elizabeth and Philip, who married at Westminster Abbey in 1947, are due to celebrate their platinum, or 70th, wedding anniversary in November.
Both the queen and Philip have suffered some health issues in recent years.
The queen missed a traditional Christmas church service last year for the first time in decades because of a heavy cold and was hospitalized in March 2013 with symptoms of gastroenteritis.
Philip underwent "an exploratory operation following abdominal investigations" in 2013.