Royal expert Nick Bullen believes that Prince Harry and his wife Meghan Markle are closely following in the footsteps of his great-granduncle Edward VIII and his wife Wallis Simpson, and might meet the same fate of going out of the limelight over the next decade.

Harry and Meghan's exit from the British royal family is often compared to that of Edward and Wallis. While Harry quit as a senior royal over alleged unfair treatment of his wife by British media and Buckingham Palace, King Edward abdicated the British throne within a year of his rule to marry Wallis, who was not accepted as the future queen by the British monarchy as well as by Parliament for being twice divorced.

Meghan and Wallis are repeatedly compared to each other as both were 30-something American divorcees, and celebrities in their own right when they married British royals who stepped down from their royal duties. While Wallis had two husbands before Edward VIII and was married when she fell in love with the then-future king, the "Suits" actress was married to Trevor Engelson from 2011-2013 before she met Harry. Meghan and Wallis are also the only royals who were allowed to keep their Duchess titles but barred from using their Her Royal Highness honours.

Bullen, CEO of True Royalty TV, told Fox News that Harry and Meghan risk becoming "bit players" and "awkward guests" at dinner parties in New York like Edward VIII and Wallis Simpson, and could "fade into obscurity" over the next decade if they continue to alienate themselves from the royal family. The royal filmmaker, who has ties with the royal family, was discussing the release of one of his programmes exploring the similarities between Harry and Edward VIII.

"It may seem far from now, but it will happen. What will happen to Harry and Meghan ten years from now? Will they be the same stars they are now? Some historians have suggested that this is unlikely," Bullen said, adding that the fact that Edward and Wallis Simpson fell out of favour is a stark warning to the Sussexes.

The filmmaker said that Harry and Meghan are high-value commodities in the showbiz world now, launching one project after another, including Harry's recently announced memoir. However, he noted that Edward, who had moved to France with Wallis after he abdicated the throne had also penned a memoir "A King's Story" in 1951.

"How long will Harry and [his wife] Meghan Markle's value stay at such a high level?" he said.

The documentary maker also claimed that contrary to Harry, who has gone all out against Buckingham Palace and is likely to be critical of them in his biography as well, Edward was more at ease with abdication. He liked to say he still wanted to be king, but never regretted forsaking the throne in favour of marrying Simpson.

Royal historian Robert Jobson told Mail Online that Edward's book was "much more important" than the memoir which Prince Harry is set to publish next year – because as an ex-King, the Duke of Windsor "had more gravitas" than the Duke of Sussex.

Edward VIII and Wallis Simpson
Edward VIII and Wallis Simpson Getty/Central Press