The Duke of Edinburgh represented the King at former U.S. President Jimmy Carter's funeral in Washington, D.C. this past week. He is seated next to the U.N.'s Secretary-General and Princess Mabel, the widow of Prince Friso, brother of King Willem-Alexander of the Netherlands. Prince Friso died years ago due to an avalanche while skiing. Princess Mabel has been active in a charity with Pres. Carter. It had to do with eliminating forced child marriages and rights of women. Princess Mabel was much in the news after Prince Friso's death, but has not been as visible in recent years.
https://www.townandcountrymag.com/society/tradition/a63384395/princess-mabel-jimmy-carter-funeral/