Kate Middleton is ready to swallow a bitter pill for Prince William as cancer-stricken King Charles makes big plans to succession plans.

The monarch, who is still undergoing treatment, is now speeding up his succession plans by five years, but the Prince and Princess of Wales may not be keen on it, according to a royal biographer.

Princess Kate, who completed her cancer treatment after gruelling nine months, is now easing back in to her royal duties, while William is quietly stepping up in his royal role.

However, while no one is willing to entertain the thought, there is also a part played by Prince Harry in an event King Charles and Prince William cannot take over, royal author Tom Quinn said.

“Because King Charles has cancer, succession planning is taking place right now – at least five years earlier than originally envisaged and it is focused on getting William and Kate up to speed,” he told The Mirror.

“No one is taking seriously, yet, the idea that William might not be able to take over because William being out of the picture is the nightmare scenario that nobody wants to contemplate,” Quinn continued.

He added that while Kate would “hate” the idea of his estranged brother-in-law as regent, but she would not resist or stand in his way.

“Kate would hate the idea that Harry might be regent with Meghan by his side but she is very pragmatic,” he explained. “And if the royal machine said ‘do it’ she would do it. Her image as the dutiful, uncomplaining princess is one she will not want to lose.”