Charles Spencer, the younger brother of the late British royal Princess Diana, is writing a book about her life and his personal memories of her. Titled “Swan Song: Diana, My Sister,” the book is due to be published in the United Kingdom next month, ahead of the 30th anniversary of Diana’s death. Michael Joseph, an imprint of Penguin Random House, will publish it in the UK before releases in other countries.

Spencer said that over time, much misinformation about Diana has become accepted as truth. He said he regularly receives requests for interviews about his sister and finds some published opinions about her uncomfortable because, in his view, many are untrue. He decided to present his thoughts and memories in book form, drawing on his own experiences and relationship with Diana.

Diana gained global recognition after marrying the then Prince Charles in 1981 and became one of the world’s most photographed women. Their marriage ended in divorce in 1996, and she died aged 36 in a Paris car crash in August 1997. Penguin Random House publishing director Daniel Bunyard called the planned book a work of historical importance.