Princess Diana and David Bowie at Wembley Arena in London for the Concert of Hope on World AIDS Day on Dec. 2, 1993. Can't get enough of PEOPLE's Royals coverage?

Princess Diana and David Bowie at the Concert of Hope benefit for World AIDS Day at Wembley Arena in London on December 2, 1993. | Credit: Tim Graham Photo Library via Getty Images.

David Bowie, Alan Rickman, the husband and brother of Celine Dion, and most recently, Eagles’ guitarist Glenn Frey. Some years ago, I collaborated to produce the book “ Mourning Diana .” ...