Writing for the Daily Mail, royal author Robert Jobson revealed that Zara Tindall "can tell the heir to the throne he is being pompous" - and does not hold back. The Prince of Wales, 44, simply "just takes it," the author said.
Zara, a down-to-earth equestrian, has a unique bond with William that goes back to childhood. Born just 13 months apart, the cousins shared summers at Balmoral, Christmases at Sandringham and rainy afternoons left to their own devices while the adults were busy.
She knew him before he was a headline
Mr Jobson said Zara "has no angle" in keeping the future monarch grounded. "She knew him before he was a headline," he said, explaining that she watched "a boy she had grown up with become public property inside a week" after William's mother died in 1997.
Zara offered the same down-to-earth treatment to Catherine when she joined the Royal Family. Mr Jobson said Zara "did the same for Catherine, who married in from outside the tent and found waiting there a woman who had spent her whole life declining to be impressed by the tent."
A Balmoral incident with a go-kart
Their close bond has produced moments of royal chaos. William once recalled a childhood blunder at Balmoral involving Zara, a go-kart and Queen Elizabeth II.
Speaking on the Our Queen at Ninety documentary, William said: "We were chasing Zara around, who was on a go-kart, and Peter [Phillips] and I managed to herd Zara into a lamppost. And the lamppost came down and nearly squashed her! I remember my grandmother being the first person out at Balmoral running across the lawn in her kilt... she came charging over and gave us the most almighty b*******."
A godmother and a sister
Today, William and Zara remain close, often seen laughing and hugging at events such as Royal Ascot. William chose Zara to be Prince George's godmother - the only member of the Royal Family to hold that title for his children.
Royal expert Ingrid Seward told Hello! magazine that Zara acts as the "sister William never had" because she holds no official royal title. Her mother, Princess Anne, intentionally declined HRH titles for her children to give them a chance at a normal life.
"She has the best of both worlds," Ms Seward said. "She understands what royal life is like, but she can live her life as she chooses, without the pressure faced by more senior royals."
