Thursday marks what would have been Prince Philip’s 100th birthday. The Queen will be spending the day reflecting on the extraordinary life of her husband, and the impact he made during his long life. Prince Philip died on April 9 at Windsor Castle – just a couple of months before his 100th birthday. Before his death, Buckingham Palace was considering the best way to mark Prince Philip’s birthday, which he would have wanted to be a low key affair.. Royal commentator for Sky News, Alastair Bruce, said: “The Duke of Edinburgh was never much interested in birthdays himself. Still less, being a 100.