It is important to note that the real name of the Duke of Sussex is not Prince Harry; this is only a diminutive that his mother used to refer to him with great affection, but it became so popular that to this day everyone still calls him that way; however, Princess Diana on special moments referred to him in another way, according the press.
Officially from a legal point of view, the youngest son of King Charles III and the late Princess of Wales is named Henry Charles Albert David Windsor, and according to the media, Vanidades, this is the name his mother used to refer to him when she required his full attention or when she wanted to talk about a serious matter.
For formal matters, documents, or even speeches, the Duke of Sussex uses his original name, Henry; however, he is known worldwide as ‘Harry’, being this the way in which most of the media refer to him; this is due to Diana, who repeatedly called him Harry, popularizing the nickname.
During interviews, public events, and day-to-day life, Princess Diana would refer to her youngest son as Prince Harry, assuring that she would only use his real name under very important circumstances. The Sussex understood that and knew that when he heard ‘Henry’ from his mother, he should listen carefully as it was something serious.