Kate taking helicopter with George, Charlotte and Louis sparked 'tense clash' between Charles and William

Robert Jobson's soon-to-be-released biography, Catherine, The Princess of Wales, claims that the King, 75, “raised concerns” with William, 42, over his helicopter use with Kate and their children, Prince George, Princess Charlotte and Prince Louis.

According to Jobson, these concerns sparked a “tense disagreement” between the father and son.

In an excerpt from Jobson’s book, King Charles brought up his worries after learning about his cancer diagnosis, which was announced in February.

The King presented experienced pilot William with “a formal document acknowledging the risks involved and taking full responsibility for his actions”, the new book has claimed.

Charles’s concerns echoed that of his late mother Queen Elizabeth II, who previously requested William not fly with his family on a helicopter from Kensington Palace to his countryside residence of Anmer Hall in Norfolk, which is a 115-mile journey, according to Jobson.

Queen Elizabeth II “didn’t hold back” on her opinion, an aide shared in the new book, after the 1967 helicopter crash that killed her flight captain.

Buckingham Palace does not comment on private conversations or His Majesty's views, but they do take into account the safety and security of others when deciding on the most appropriate means of travel for the Royal Family.

It is also understood the Palace has fully evaluated the risk of the family flying together.

Elsewhere in the book, Kate, 42, who is currently receiving cancer treatment, is praised as having a “stabilising influence” on William.

The commentator claimed this is particularly true when it comes to tensions between the prince and his father.

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A source told Jobson that Kate “is somebody who always tries to see both sides of any dispute” and is the “emotionally mature” one in their relationship.

King Charles also values Kate’s positive effect on his eldest son, according to the book.

“I think the [King] understands Catherine is a good influence on the entire family. He loves and truly appreciates everything she does,” a courtier said.

Catherine, The Princess of Wales will be available to purchase on August 6.