Lady Diana biographer Andrew Morton (69) is full of praise for Elizabeth Debicki's (32) portrayal of Diana in the fifth season of "The Crown". This "takes his breath away" and "takes him back to all those years ago," he told Good Morning America. "I don't say that very often, but I was shaken." Morton had written the biography "Diana: Her True Story" in collaboration with the Princess (1961-1997).

Published in July 1992, the book revealed Diana's dissatisfaction with her marriage to the unfaithful Prince Charles, 74, her struggle with bulimia, and her feelings of loneliness and depression. The work meant the end of the royal marriage, and in December 1992 Prime Minister John Major (79) announced the couple's separation. Morton and Diana's collaboration on the book is detailed in the new season of the hit Netflix series. The author was on board as a consultant and is played in the series by Andrew Steele ("Outlander"). "The writers asked me all kinds of questions, like what color the wallpaper was in my daughter's bedroom because that's where I had an office for a while," says Morton.

Morton had already praised Emma Corrin's (26) portrayal of Diana in season four of "The Crown". It's the most realistic he's seen so far, he told Vanity Fair.

"I found the preparations for the wedding very moving as both sides began to realize that they were heading towards an undesirable and unfortunate outcome, which is the royal wedding," says Morton. "It reminded me of what a close friend of Diana's had to say about the whole mess while researching Diana: Her True Story: 'I'm sorry for the tragedy this all represents. My heart bleeds for this whole misunderstanding , but it bleeds the most for Diana.'"

The fifth season of "The Crown" has been available on Netflix since November 9th.