[custom_adv] Prince Philip, Duke of Edinburgh, the oldest and longest-serving royal consort in British history, marked another remarkable milestone on Wednesday: He turned 99. As usual, he didn't want a fuss. The husband of Queen Elizabeth II celebrated at Windsor Castle, where both he and the queen have been self-isolating since mid-March amid the coronavirus pandemic. [custom_adv] A newly-released photo taken June 1 and shared by the palace in honor of his birthday shows him and the queen posing together in the quadrangle of Windsor Castle: The Queen wearing a cream and yellow floral Angela Kelly dress with the Cullinan V diamond brooch, while Philip wore a Household Division tie. [custom_adv] Due at least in part to the pandemic, which still has much of Britain in its grip, his birthday was a low-key affair at the castle, where the monarch and her consort planned to share lunch and spend the day together. [custom_adv] He was expected to take Zoom and phone calls from his many relatives in self-isolation elsewhere; he and the queen have four children, eight grandchildren and eight great-grandchildren. [custom_adv] Prince Philip, the husband of Britain's Queen Elizabeth for more than seven decades, celebrates his 99th birthday on Wednesday, although there will be little public fanfare to mark the occasion. Philip, the Duke of Edinburgh, will spend the day privately at Windsor Castle, west of London, where he and the 94-year-old monarch have been staying during Britain's coronavirus lockdown. [custom_adv] He stepped down from royal duties in August 2017 after completing more than 22,000 solo engagements but in recent years he has been increasingly rarely seen in public. [custom_adv] His full title is HRH The Prince Philip, Duke of Edinburgh, Earl of Merioneth and Baron Greenwich, Knight of the Garter, Knight of the Thistle, Order of Merit, Knight Grand Cross of the Order of the British Empire, Companion of the Order of Australia, Companion of The Queen's Service Order, Privy Counsellor.