The Queen feared Princess Diana was too shy to handle her 1983 tour of Australia and New Zealand alongside Prince Charles.
But now archives have revealed how Diana really felt about her visit, despite alarm over protesters as the royal couple arrived in Wellington, reports the Daily Mail.
Charles and Diana were "mooned" by well-known Māori protester Dun Mihaka as they drove into the city from the airport.
A "confidential" document written by the former New Zealand High Commissioner Sir Richard Stratton to the Foreign and Commonwealth Office recalled the incident.
"The professional, mainly white, protesters made little impact. A well-known Māori agitator presented his bare bottom (allegedly the worst Māori insult, but I have my doubts!) to Their Royal Highnesses as they drove into Wellington from the airport."
Police had been told Mihaka was planning a whakapohane (baring of the buttocks) when the royals arrived in Wellington. As the royal motorcade left the airport, police officers recognised him and arrested him.
The Prince and Princess of Wales set out on the official tour after welcoming their son Prince William, now 38. Diana, then 22, divorced from Charles in 1996. She died tragically just a year later at the age of 36 after a fatal car crash in Paris.
According to a report in Vogue at the time, the royals were concerned that Diana wouldn't be able to handle the intense pressure of a royal tour.
The Press Association's royal correspondent Grania Forbes wrote, "The Queen is 'terribly worried' before the tour because of Diana's youth and apparent shyness."
But now archived files recently released under the UK's Freedom of Information Act have revealed that the Queen had nothing to worry about - Diana charmed the nation and won over countless fans during her visit.
The commissioner pointed out that "New Zealanders wanted above all to see the Princess of Wales, and they did, especially in the numerous 'walk-abouts'.
"Princess Diana's clothes and homely (in the best, English sense) gestures towards children and Prince Charles's witty speeches won particular acclaim."
And a debrief after the tour noted: "There is no doubt that this royal visit has been a personal triumph for the Prince and Princess of Wales, both individually and together.
"In the process it has provided striking evidence of the depth and warmth of feeling which Australians have for their royal family, and of their loyalty to the Crown."
The documents are kept in Britain's National Archive files and in a Freedom of Information release by the Foreign, Commonwealth and Development Office.