Britain's Prince Philip, the 99-year-old husband of, underwent a procedure for a preexisting heart condition on Wednesday. He will while he recovers, Buckingham Palace said in a statement Thursday.
"His Royal Highness will remain in hospital for treatment, rest and recuperation for a number of days," the palace said. The surgery took place at St Bartholomew's Hospital.
The, the wife of Philip's son Prince Charles, said that the Duke of Edinburgh was "slightly improving."
"We'll keep our fingers crossed," Camilla told Britain's Press Association news agency.
Philip was first admitted to King Edward VII's Hospital in London in mid-February, before being moved to St Bartholomew's earlier this week. The royal, who celebrates his 100th birthday in June, has now spent 16 days in the hospital, marking his longest-ever stay.
Last week, their youngest son Prince Edward said his father was "a lot better." Prince William also previously said his grandfather was "okay" and that the hospital is "keeping an eye on him."
Prince Philip has been treated for heart problems in the past. In 2011, he was taken to a hospital by helicopter after experiencing chest pains in Sandringham. At the time, he was treated for a, undergoing a minimally invasive procedure of coronary stenting.
The royal family has facedin recent weeks, ahead of Prince Harry and Meghan Markle's with Oprah Winfrey, airing Sunday on CBS. In a , Markle said that she could not be expected to stay silent if the palace is "perpetuating falsehoods" against her.
Last month, the Duke and Duchess of Sussex announced they will not be returning as working members of the royal family, formally stepping away from their royal duties.