India, Aug. 4 -- Royal biographer Catherine Mayer has argued that the rupture which saw Meghan Markle and Prince Harry step back from royal duties inflicted lasting harm on the British monarchy, as the Duchess of Sussex marked her 45th birthday on Monday.

Mayer, author of the new book "Divide & Rule," told Fox News Digital that the split which took Harry and Meghan to the United States, has caused very serious damage to the monarchy, though she stressed this was not intended as an accusation against the couple themselves, noting that recent polling shows the institution's popularity continuing to slide.

Meghan Markle News: Why Does One Author Say The Monarchy Lost Its Connection With Younger Audiences?

Mayer argued that while much of t...