Queen Elizabeth II’s 99-year-old husband Prince Philip has undergone a successful heart procedure, Buckingham Palace said after he was transferred to a cardiac unit in London. Royal officials said the Duke of Edinburgh, as he is formally known, “underwent a successful procedure for a pre-existing heart condition at St Bartholomew’s Hospital” on Wednesday. “His Royal Highness will remain in hospital for treatment, rest and recuperation for a number of days,” they added. Philip has now spent more than two weeks in hospital, his longest every stay, raising fears for his health because of his advanced age. He will turn 100 on June 10. He was first admitted to the private King Edward VII Hospital in central London on February 16. Buckingham Palace said initially that he was expected to stay there for a “few days” after walking in unaided. His illness is not believed to be related to the coronavirus. Both Philip and the monarch received COVID-19 vaccinations in January and chose to publicize the matter to encourage others to also take the vaccine. He has had heart issues in the past. In 2011, he was rushed to a hospital by helicopter after suffering chest pains and was treated for a blocked coronary artery. Philip’s daughter-in-law Camilla, Duchess of Cornwall, said Wednesday he was “slightly improving” but he “hurts at moments” and the royal family is keeping its fingers crossed for the hospitalized duke’s recovery.