In a video interview released on Monday with the Canadian news programme "The National", the daughter of the late Queen Elizabeth II discussed the kind of monarch the King will be.
"I don't think he'll change. You know what you're getting because he's been practising for a bit," she said.
"He is committed to his level of service, and that will remain true."
Princess Anne also said her brother's plan to reduce the size of the monarchy once he becomes King of England is 'not a good idea.'
"The slim down was said on a day where there were more people around to make that sound like a justifiable comment...it doesn't sound like a good idea from where I'm standing, I have to say. I'm not sure what else we can do," said the British royal during an interview with CBC released on Monday.
In several interviews, Prince Charles has expressed a desire to reduce the number of working royals.
While Charles has seen an increase in his popularity rating in recent months, surveys tracking long-term sentiment towards the royals showed support for the monarchy to be at a record low
In recent years, such surveys have repeatedly shown an increasing divide between the generations, with young people far less supportive or just ambivalent about the monarchy.
Backing for the royals has declined over the last few years amid a period of turmoil for the family.
There has been the departure from the royal roles of Prince Harry and his wife Meghan, and their subsequent criticism of Buckingham Palace and even allegations of racism.
Meanwhile, allegations of sex abuse levelled in the United States against Elizabeth's second son, Prince Andrew, which led to him settling a court case, have also proved highly damaging, despite his denial of wrongdoing or any criminal charges. The furore meant he too was forced to quit his royal role.
The 74-year-old monarch was the oldest sovereign to take the throne in a lineage that dates back 1,000 years when he succeeded his hugely popular mother Queen Elizabeth after her death last September. She had reigned for 70 years.
On Saturday, Prince Charles will become officially become King Charles III during an elaborate ceremony with royalty from all over the world in attendance.
After the coronation ceremony, Charles and his wife Camilla will ride in a 260-year-old gold-plated coach in a parade with 5,000 men and women from British and Commonwealth armed forces.
More than 2,200 people will attend the coronation of Britain's King Charles, Buckingham Palace said, including international representatives from 203 countries as well as community and charity workers.
The palace has been steadily releasing details of Charles' coronation, which is set to be smaller in scale than that of his mother in 1953 but still replete with pomp and pageantry.
Reuters