The Duke of Edinburgh has been admitted to hospital in central London for planned surgery on his hip, Buckingham Palace has said.
The surgery will take place on Wednesday at the King Edward VII Hospital in Marylebone.
Prince Philip, 96, retired from royal duties last August.
The duke did not attend the Easter service at Windsor Castle on Sunday, with his absence said to have been because of a hip problem.
He also missed two other events at Windsor in recent days – last Thursday’s Royal Maundy Service and a parade on 22 March to mark Prince Andrew’s appointment as Colonel of the Grenadier Guards.
In a statement, Buckingham Palace said: “His Royal Highness The Duke of Edinburgh was admitted to King Edward VII Hospital in London this afternoon, for planned surgery on his hip which will take place tomorrow.
“Further updates will be issued when appropriate.”
The duke announced his retirement in May 2017, after decades of supporting the Queen, as well as attending events for his own charities and organisations.