Tom Bower, a royal biographer, believes it has become "impossible" to contain the rift between the Sussexes and the rest of the British Royal Family.

Express UK reported that Tom Bower recently made the claims. It comes after the release of his new book, "Revenge: Meghan, Harry and the War between the Windsors," wherein he printed several assertions about the former working royals.

In one of his latest engagements, the author reportedly deemed the situation among the British Royals "toxic." He is also said to have asserted that despite the Prince of Wales and the British Monarch's effort to "do their best" and "keep it cool," it is "just impossible" to do so.

The publication did not dwell on the details of the claims, or whether the expert expounded on his statements.

It, nevertheless, quoted the biographer, saying, "But, ever since Meghan left Britain, and then did the Oprah Winfrey [interview], it has been really poisonous."

Bower consequently noted that this comes at a time when the Duke of Sussex's memoir is about to come out.

It remains unclear when the royal-born Prince's memoir will become available to the public. But, it is believed that the material will officially surface on the market later this year.

There have been several speculations about the content of the book since the news broke that Prince Harry will drop his memoir. Some even asserted that he could "target" the wife of Prince Charles, his stepmother, Camilla Parker Bowles.

Earlier in April, a source told The Telegraph that the Duke of Sussex "needs a new target and [the Duchess of Cornwall] will do."

It was also alleged that the former working royal "will say some unkind things about her, or try to make her a 'baddy,' but that does not mean it's real."

Mail Online later quoted the insider, claiming, "If the strategy is to create drama, this creates drama."

Meanwhile, another royal expert previously stated that the British Royal Family, including Prince Charles and the Sussexes, might have missed the opportunity to heal the ongoing rift among them. It came after Prince Harry and Meghan Markle did not attend most of the events during the Platinum Jubilee celebrations, according to a separate report from Express UK.

Speaking to "Sunrise," Victoria Arbiter said that the absence of the former working royals was "quite telling." She explained that some individuals were hoping for the pair to stay in the United Kingdom for a couple of days, possibly allowing them to have "private bonding time" and "opportunity... to talk through their difficulties."

However, the Duke and Duchess of Sussex left the country hours before the conclusion of the historic celebration. This led the expert to assert that the "tension" between the two parties was still "ongoing."