The tour across southern Africa begun Monday by Prince Harry, Duke of Sussex; Meghan, Duchess of Sussex; and their son, Archie Mountbatten-Windsor, will surely be as modern as they are — but Prince Harry’s plan for Thursday and Friday will also echo the past. Harry will honor Princess Diana’s advocacy against landmines in Angola by making a trip very similar to the one his mother made in January of 1997, when she walked across a minefield in Huambo in central Angola. The photographs of Princess Diana wearing protective clothing and equipment, as well as her meeting landmine survivors, raised the profile of the work being done to clear landmines around the world.