Prince Philip has been taken to hospital for an exploratory operation following abdominal pains.
He is expected to remain at The London Clinic in Harley Street for around two weeks.
Buckingham Palace said in a statement: "His Royal Highness The Duke of Edinburgh has been admitted to the London Clinic for an exploratory operation following abdominal investigations.
"He is expected to stay in hospital for up to two weeks. Further updates will be issued when appropriate."
His was driven to hospital shortly after attending a garden party at Buckingham Palace where he appeared to be in good spirits.
The Duke, who turns 92 on June 10, had missed an engagement at the palace on Monday night because he was feeling "under the weather"