Prince Harry and Meghan Markle stepped back from their roles as senior royals in January 2020, as they were convinced that the 'entire institution' was against them.
Royal author Andrew Morton believes that out of all the possible reasons for their departure, there's one picture in particular that could have been a "wake-up call" for them.
Even before they stepped down, Harry and Meghan had reportedly long believed that The Firm were "conspiring against them". This argument came to a head when the Royal Family released an official photograph which showed the late Queen and her heirs, King Charles, Prince William and Prince George, the Mirror reports.
The picture was released in 2020 just days before Harry and Meghan announced that they were stepping down.
Upon looking at the photo, it seems as though it simply lined up the future of the monarchy, like many pictures in the past had done. But it apparently caused difficulties at Buckingham Palace, according to the royal author.
In his book Meghan: A Hollywood Princess, Morton wrote: "The royal couple suspected that the entire institution was conspiring against them. As they saw it, the evidence was all around them.
"The unspoken code was straightforward: the future of the monarchy was assured, with or without Meghan and Harry."
Harry then cancelled a meeting with the Queen during which they were supposed to talk about his royal future, Andrew claims.
"This sense that, despite their international popularity, they were low down the royal totem pole was confirmed when Harry arranged to meet the Queen for a grandson-to-grandmother chat in early January.
"At the last minute the meeting was postponed. Pod Save the King suspected classic internal politics, his family concerned that anything the Queen agreed during informal conversations would be used by Harry as a negotiating tactic."
Speaking to The Mirror's podcast 'the Commonwealth.', Morton revealed that Harry and Meghan had started to think about leaving The Firm far earlier than the public thought and said talks began just six months after their wedding.
Morton told the podcast: "Harry was having conversations in a London hotel with Oprah Winfrey back in November 2018, just six months after they'd been married. So they were thinking about a different direction of travel pretty early on.
"The irony is they had been given the keys to the first class lounge when Prince Harry was given the position of Youth Ambassador to William and Catherine.
"This was effectively the Queen's way of saying 'you do the rest of the world, leave Royal Family to do the UK where they will eventually be the Heads of State.'"
The couple announced that they would be stepping back from their roles as senior royals in January 2020, after "many months of reflection and internal discussion".
Don't miss the latest news from around Scotland and beyond. Sign up to our daily newsletter here.