Morton, from Dewsbury, was covering the Queen’s visit to San Diego and he became fascinated by the Royal Yacht Britannia. As a history graduate he wanted to know more about the famous boat and thought he’d read up about it, but when he couldn’t find much he decided to write his own book.
“It looked so beautiful that I thought I’d write about it and that was the start of my journey,” says the 63-year-old.
Former national newspaper journalist and Royal Correspondent for The Daily Star, Morton is best known for his explosive biography of Diana Princess of Wales.
Diana: Her True Story, published in 1992, blew the perceived “fairytale marriage” of Diana and Prince Charles apart as it revealed Charles’s affair with Camilla Parker Bowles, Diana’s battle with the eating disorder bulimia and her attempted suicide by throwing herself down the stairs.
Morton was vilified as people reacted angrily to the revelations, exacerbated by his refusal to name his source.
It was only after her death that Morton revealed it was Diana herself, who had not only authorised the book, but had given him most of his information.
“I was nervous about it. We were discussing things that had never been talked about before.
"Everybody had bought into the fairytale of Charles and Diana and the book was going to show that just wasn’t real. It remains the book I am most proud of.”
At the time most national newspapers refused to serialise it and Morton himself was threatened and his offices ransacked. He was dubbed the “tabloid vulgarian from Leeds”.
“It’s ironic that the person who said it was a fairytale wedding – the Archbishop of Canterbury – later admitted thinking the marriage was not going to work,” he said.
The book caused uproar within the Royal family and pain for the Queen who, Morton agrees, has done her best to keep her family together.
It led to Charles giving his televised interview with Jonathan Dimbleby in which he admitted his adultery in 1994, followed a year later by the infamous Diana interview for Panorama with Martin Bashir.
In his latest book, called simply The Queen, published to coincide with her Platinum Jubilee this week, some say Morton is atoning for his revelation 30 years ago.
“I do find it a bit ironic that people say this is some sort of atonement for the Diana book,” he said.
“That book was her story and it was written with her full co-operation and from her point of view.
“What I wanted to explore in this book was the Queen as a human being, the woman behind the mask, as opposed to the public face that we all see,” says Morton, who started writing The Queen two years ago, only putting the finishing touches to it quite recently to ensure that it is as up to date as possible.
“What did strike me while writing this book is how much more relaxed the Queen has become over the last few years of her reign. She seems to be really enjoying being Queen,” he says,
He has written about the Queen before in a book about the relationship with her sister Princess Margaret.
And he says of all the challenges the Queen has faced over the 70 years of her reign, her family has been the biggest.
“Over the years I have asked numerous people who is the Queen’s favourite child and they always come back saying Andrew,” says Morton, who divides his time between London and America, where his second wife is from.
“It must have been appalling for the Queen to have her favourite son embroiled with the Jeffrey Epstein affair. And then his terrible lack of judgement giving that Newsnight interview will have been very difficult for her, although the Queen and Princes Charles approved it. It showed a real naivety and was utterly baffling.
"It seems to me that the Royal family are better steering clear of television cameras when it comes to interviews.”
Andrew Morton was born and brought up in Yorkshire. His father, Alec, ran a picture framing and art materials business in Dewsbury.
He went to Temple Moor Grammar in Leeds, then to Sussex University where he studied history and developed an interest in aristocracies and elites.
“I always thought I’d become an academic,” he says. “But then I decided to become a journalist instead.”
He enrolled on the Mirror Group training scheme alongside the likes of Alastair Campbell and crime writer Val McDermid, before getting jobs at the Daily Star, News of the World, and Daily Mail. He went freelance in 1989.
It was while he was at the Daily Star that he started to write about the Royals.
“James Whitaker had moved from the Daily Star to the Mirror and they needed someone to cover the Royal Family. They thought I looked presentable and I’m tall so I could look over the top of other people,” he said.
He wrote a number of royal books, including Andrew The Playboy Prince, before he started researching his Diana book in 1990.
He asked Dr James Colthurst – a mutual friend – if he would ask Diana if she’d consider giving him an interview – not really expecting her to say yes.
“I’d been writing some sympathetic and positive things about their marriage unbeknown to me and the rest of the country what was really going on – and I think it struck a chord and so she offered me an interview. How can you say no to the Princess of Wales?
"I didn’t know about things like the bulimia and Camilla Parker Bowles, it was all new terrain.”
It was only after her death that Morton revealed she was his source and that he had hours and hours of tapes of her interview.
He was further castigated for releasing an updated version of Diana: Her True Story despite giving much of the profits to charity.
It is not the only controversial book Morton has penned. His unauthorised biography of Tom Cruise, which was never released in the UK due to our strict libel laws, saw him in hot water with the actor and the scientology movement to which Cruise belongs.
However, his biography of Her Majesty The Queen is far less revelatory and is much more sympathetic in tone.
“She is very much a caring grandmother, she is very stoical and she’s always tried to keep the family together.
"It is remarkable to think that Prince William would have been on the throne for 15 years had he inherited the Crown at the age she did,” reflects Morton.
“I also believe that William sees being the Monarch very much as a job, rather than a vocation, and I think that is a good thing.”
The Queen by Andrew Morton is published by Michael O’Mara Books, priced £20.