Prince Harry and Meghan Markle are only expected to cause more troubles following their exit -- and they could even kill the monarchy.

The Duke and Duchess of Sussex will finally mark their last day as members of the royal family on March 31. From that day onward, they will no longer enjoy the royal perks which they have enjoyed before.

Though their departure would mean less expense for the monarchy, it negatively echoed the statement made by Sir David Attenborough years ago about the danger of shifting from being royals to becoming "ordinary" and revealing so much about royal life.

Following the release of the palace's 18-month-old 1969 documentary "Royal Family" that year, Sir Attenborough responded to the series and said that it exposed too much information about the monarchy.

"You're killing the monarchy, you know, with this film you're making," the documentary maker uttered. "The whole royal institution depends on mystique and the tribal chief in his hut."

He pointed out that if any member of the tribe sees everything inside the hut, the whole chiefdom's system becomes damaged and gradually loses its strengths.

Thus, like the tribe he mentioned, the monarchy could receive a ticking bomb upon completely losing Prince Harry and Meghan and letting the two damage the royal family's foundation.

In addition, even the royal author Ingrid Seward wrote in her 2000 book "The Queen and Di: The Untold Story" seconded Sir Attenborough's warning for the royal family.

She said, "It was a warning which was ignored, and, in retrospect, the program came to be seen to have given fateful encouragement to exactly the kind of intrusive interest in their lives which the Royal Family were at such pains to avoid."

Sussexes Will Be Ordinary Upon Breaking Away

In January, The Atlantic's Tom McTague claimed that the Duke and Duchess of Sussex can fully decide for themselves starting next month after they successfully shooed off royal neutrality.

McTague added that since they chose to have ordinary lives, they will soon start to behave like normal people. Because of this, people will treat the soon-to-be-former-royals as ordinary.

Previously, Valentine Low, the Times of London's royal correspondent, also compared the two with the Duke and Duchess of Windsor.

According to Low, the royal couple of Windsor became unimportant people after the Duke renounced his throne. What they feared that time could also happen to Prince Harry and Markle.

As part of their transition, they can no longer be able to use their HRH titles starting next month. Moreover, from that day onwards, they will be funded by Prince Charles' Duchy of Cornwall estate and will officially no longer be senior members of the royal family. 

Despite these changes, Prince Harry expressed his excitement to the Russian hoaxers, Vladimir Kuznetsov and Alexey Stolyarovi (who pretended to be the young climate change activist, Greta Thunberg and her father Savante) in a leaked hoax phone call earlier this month.

Harry said that he is "much more normal than my family believes" and that he and Meghan are excited about finally getting away from the royal restrictions soon -- even if that means damaging the monarchy.

READ MORE: Royal Shame: Prince Harry, Meghan Markle NOT Welcome To Return To U.K. [POLL]