Prince Philip is recovering in the hospital after undergoing “successful” surgery for his heart condition, Buckingham Palace said on Thursday.

A spokesperson for the palace said of Queen Elizabeth's husband: “The Duke of Edinburgh yesterday underwent a successful procedure for a pre-existing heart condition at St. Bartholomew's Hospital. His Royal Highness will remain in hospital for treatment, rest and recuperation for a number of days.”

The 99-year-old was transferred to St. Bartholomew's after spending almost two weeks at King Edward VII hospital. In 2011, he underwent surgery to insert a coronary stent and relieve a blocked artery.

Meanwhile, the Royal Family is reportedly awaiting Meghan Markle and Prince Harry‘s interview with Oprah Winfrey this Sunday with trepidation. A source told ET that they have been in touch with the Palace, but “things are tense. And while Harry loves his grandmother and grandfather, the timing of the Oprah interview has complicated matters.”