Princess Anne believes the Queen was totally correct in her decision remain at Balmoral with Princes William and Harry in the days after Princess Diana's death.
The Princess Royal said her mother did "exactly the right thing" by not returning in the immediate aftermath of the fatal Paris crash in 1997.
Her absence from London, where millions had gathered to lay flowers and pay tribute to the late Princess, frustrated the public who questioned why the sovereign wasn't publicly mourning Diana.
Many believed Her Majesty should have returned from Balmoral before she did bow to public pressure, coming back to Buckingham Palace a day earlier than planned to address the nation.
Some royal commentators suggested it was the only mistake of her incredible reign, but the Queen's daughter disagreed and claimed her beloved mother didn't misjudge the mood.
The 72-year-old spoke to ITV's Chris Ship back in 2017, an interview which has been broadcast for the first time.
Speaking before the death of both the Queen and her husband Prince Philip, Anne also praised her parents' 73-year marriage, saying their partnership was "really important".
She said: "I think my mother did exactly the right thing. I think it's absolutely extraordinary that any right-minded parent should believe... [there] would have been an alternative to bring those children down here to London in all that hoo-ha.
"I just don't know how you can think that would've been a better thing to do."
William was 15 and Harry 13 when they lost their mother on that terrible night in the French capital.
Asked if it was a case of the Queen putting her grandchildren first, the Princess Royal responded: "Absolutely
"I don't think either of those two would've been able to cope had they been anywhere else," Anne said.
"If you were the grandmother of a 12-year-old and a 15-year-old whose mother had just been killed in a car crash, she did absolutely the right thing.
"If I had been her, I would have done that. Why would you bring them to London? Why don’t you let them get over the start of the shock in the bosom of their own family?"
Princess Anne will accompany the Queen's coffin on a flight from Edinburgh to London, arriving later today.
The cortege will then travel to Buckingham Palace where the oak casket will be met by King Charles, the Queen consort and other members of the royal family.
At 2.22pm on Wednesday, the coffin will be taken on a gun carriage of The King’s Troop Royal Horse Artillery to the Palace of Westminster.
Accompanied by the sound of minute guns fired from Hyde Park by The King’s Troop Royal Horse Artillery, the cortege will make a trip past London landmarks.
It will travel via Queen’s Gardens, The Mall, Horse Guards and Horse Guards Arch, Whitehall, Parliament Street, Parliament Square, and New Palace Yard.
The Queen will lie in state until 6.30am on the day of her state funeral on Monday.
