Prince William and Prince Harry
Prince William and Prince Harry are pictured hosting a reception to officially open the Illegal Wildlife Trade Conference on Oct. 10, 2018 in London, England. Tolga Akmen - WPA Pool / Getty Images

Although Queen Elizabeth is the head of the monarchy, she enlisted Prince William and Prince Harry to fill in for their grandfather, Prince Philip, amid his health issues.

In the 2017 biography “Harry: Life, Loss, and Love,” author Katie Nicholl revealed Prince Philip’s health prompted Queen Elizabeth to assign Prince William and Prince Harry more royal responsibilities.

“[The Queen] knew that Prince Philip would insist on traveling with her, and, while she had agreed to carry out a tour of the British Isles to mark her sixty years on the throne, she had wisely asked her children and grandchildren to travel to the Commonwealth realms,” Nicholl said.

“For the first time, William – with Kate by his side – and Harry would have a significant role,” she added.

Luckily the Queen’s plan received a positive response from the public who were eager to learn more about the younger generation of royals. “Harry-mania swept across the Caribbean, where the prince was a huge hit,” Nicholl wrote.

Queen Elizabeth also took up with the matter with her staff and told them not to overwhelm her with royal obligations. “The Queen was well aware that despite his remarkable energy and non-negotiable sense of duty, royal life was proving increasingly strenuous for her husband,” she wrote stated.

In the past, Prince Philip was hospitalized for a bladder infection and treated for a blocked coronary artery.

“It wasn’t herself she worried about, but the Duke. His busy schedule was starting to take its toll and the Queen didn’t want Philip doing too much long-haul travel and exhausting himself,” a royal source told the author.

Going forward, Prince Charles, Camilla Parker Bowles, Prince William, Kate Middleton and Prince Harry began appearing aside Queen Elizabeth and became the faces of the British monarchy.