Meghan Markle reportedly found her walkabout at Windsor alongside Kate and William "very difficult".
The Duke and Duchess of Sussex had returned to the UK for the Queen's funeral, and appeared for a public walkabout at Windsor Castle, meeting well-wishers who had gathered to pay their respects.
According to a new royal book Our King: Charles III, by Robert Jobson, the Duchess of Sussex found the day testing for a number of reasons, including being away from her children, Archie and Lilibet.
He writes: "That's the longest they had ever been away from the kids, and then on top of it, knowing what's being said out there - it was very difficult.."
It comes after previous claims Kate found the walkabout one of the 'hardest things she has even had to do'.
Due to “ill feeling” between the senior royal couples, the Princess of Wales is said to have struggled with the time spent together, after the Queen’s death last September.
Whilst the walkabout might have come across as a symbol of unity, following the death of the centrepiece of the monarchy, Mr Jobson claimed that sources told him that wasn’t the case, according to People.
He said such togetherness was an “illusion” and he wrote: “Catherine later admitted to a senior royal that, such was the ill feeling between the two couples, the joint walkabout was one of the hardest things she'd ever had to do.”
It comes as relations between the self-exiled royals and The Firm remain at an all-time low.
At the beginning of the year, Prince Harry released his explosive memoirs Spare, where he repeatedly took aim at the Royal Family and senior members, as well.
One such claim included alleging that Prince William physically attacked him on one occasion.
In his and Meghan’s Netflix documentary a month previous, he also criticised King Charles as a father and took a swipe at other male members of the Firm for how they married.
Ahead of the upcoming Royal coronation for King Charles, whilst Harry and Meghan confirmed that they had been invited, they have not yet said if they will actually attend.
Reports suggest that the Sussexes are trying to negotiate their appearance, with The Times writing that they wanted a role for their children - including acknowledging that it was Archie’s birthday.