Prince Philip, the husband of Queen Elizabeth II for 70 years, is celebrating his 97th birthday on Sunday.
The Duke of Edinburgh was expected to celebrate in private, with no public events scheduled.
He is the oldest and the longest-serving consort in British history, described by the 92-year-old Queen as her “constant strength and guide”.
Philip, known for combining strong sense of duty with public popularity and a propensity for gaffes, has been recuperating after leaving hospital in mid-April following hip replacement surgery.
He did not join the rest of the royal family at Saturday’s annual Trooping of the Colour parade to mark the Queen’s official birthday.
Philip announced his retirement from most public duties in May 2017 and has only occasionally been seen alongside the queen since then. He appeared at last month’s wedding of Prince Harry and Meghan, the Duchess of Sussex.
The prince, who had undertaken hundreds of official duties every year, counted polo, flying and sailing among his hobbies and continued competing in horse-carriage driving competitions well into his 80s.
The Queen and Philip have four children, eight grandchildren and six great-grandchildren, including Prince George, Princess Charlotte and the infant Prince Louis, all born to Prince William and Kate, the Duchess of Cambridge.