LONDON, May 11 (Reuters) - Queen Elizabeth has been caught on camera saying Chinese officials were "very rude" during a state visit to Britain by President Xi Jinping that London had said would herald a "golden era" in relations with Beijing.
She was speaking at a garden party at Buckingham Palace on Tuesday, the same day that Prime Minister David Cameron was filmed making undiplomatic remarks to her about corruption in Nigeria and Afghanistan.
The queen's remarks may not be helpful to the British government's determined efforts to boost trade ties with China.
Under her constitutional role, the 90-year-old monarch never makes any politically or diplomatically sensitive comments in public, and it is rare for the content of her private conversations to be revealed.
In Beijing, Chinese Foreign Ministry spokesman Lu Kang said Xi's visit to Britain last year had been "extremely successful" and both countries' officials had made great efforts to that end.
In footage broadcast by the BBC, the queen is seen meeting senior police officer Lucy D'Orsi, who is introduced by an official as having been in charge of security during Xi's visit in October.
"Oh, bad luck," the queen says in response.
D'Orsi then describes her dealings with Chinese officials as "quite a testing time" and recounts that at one point they had walked out of a meeting and told her "the trip was off."
The queen says: "They were very rude to the ambassador."
Lu said he had not heard anything about Xi's visit possibly being called off at any point, adding that the visit had opened a new "golden age" in relations, brought about by both countries.
A look back at the coronation of Queen Elizabeth:
Coronation of Queen Elizabeth II - June 2, 1953
Britain's queen caught on camera calling Chinese officials 'very rude'
Queen Elizabeth II poses in her coronation attire in the throne room of Buckingham Palace in London, after her coronation, June 2, 1953. (AP Photo)
In a traditional ceremony, Britain crowned a new Queen, the Empire's first reigning woman since Queen Victoria. Elizabeth II wore the bejeweled Imperial Crown and carried the Orb, in left hand, and Scepter with Cross as she left Westminster Abbey on June 2, 1953, at the end of the Coronation Ceremony. Britain's Queen Elizabeth II celebrates her 75th birthday on Saturday, April 21, 2001. (AP Photo)
Queen Elizabeth II, wearing her crown, center foreground, leads the procession through Westminster Abbey's nave after her coronation in London, England, June 2, 1953. The Queen of England is flanked by the Bishop of Durham Rev. Arthur Michael Ramsay, left, and the Bishop of Bath and Wells High Rev. Harold William Bradfield. Maids of honor follow behind, carrying the cape. (AP Photo)
The royal carriage of Queen Elizabeth II passes along Victoria Embankment on its way to Westminster Abbey, on June 02, 1953, during the ceremony of coronation of the Queen. The Queen was solemnly crowned at Westminster Abbey in London. (Photo credit should read -/AFP/Getty Images)
The Queen's train is lifted by footman as she leaves Buckingham Palace, to enter the state coach to drive to Westminster Abbey, London, for the coronation this morning June 2, 1953, for Elizabeth to become Queen Elizabeth II. (AP Photo)
File-Coronation. The supreme moment: This is the supreme moment in the Abbey's scene of glorious and unforgettable pageantry-the moment when the Archbishop of Canterbury places the crown on the head of Queen Elizabeth II. who is sitting in the St. Edward's chair. (Ap photo/pool) 2. June 1953
Queen Elizabeth II, wearing St. Edward's Crown, is helped into throne in Westminster Abbey after her coronation in London, June 2, 1953. Aiding the young monarch are the Archbishop of Canterbury, left foreground, and the Bishop of Bath and Wells, who stands next to the Archbishop. The Queen carries in her left hand the Rod with the Dove; in her right hand the Scepter with Cross. (AP Photo)
Queen Elizabeth II sits in King Edward's chair after receiving the crown, scepter and rod from the Archbishop of Canterbury, back to camera, in Westminster Abbey in London, England, June 2, 1953. The Queen of England is flanked by the Bishop of Durham Rev. Arthur Michael Ramsay, left, and the Bishop of Bath and Wells High Rev. Harold William Bradfield. (AP Photo)
Queen Elizabeth II, dressed in the magnificent robe of cloth of gold, receives the sceptre with cross, the ensign of kingly power and justice, from the Archbishop of Canterbury, June 20, 1953. (AP Photo/POOL)
Queen Elizabeth II poses with the royal sceptre 02 June 1953 after being crowned solemnly at Westminter Abbey in London. Elizabeth was proclaimed Queen in 1952 at age 25. (Photo credit should read STF/AFP/Getty Images)
Canadian Mounted Police pass through Piccadilly Circus, London, June 2, 1953, on the processional route back to Buckingham Palace after the Coronation of Queen Elizabeth II in Westminster Abbey. (AP Photo)
The Golden Coach, with the newly crowned Queen Elizabeth II inside, passes through Trafalgar Square, London, June 2, 1953, on the processional drive following the Coronation of the Queen in Westminster Abbey. (AP Photo/Satff/Royle)
A carriage carrying The Rt Hon. Louis St. Laurent, Prime Minister of Canada, passes through Picadilly Circus, London, with members of the Royal Canadian Mounted Police during the processions following the coronation of Britain's Queen Elizabeth II, June. 2, 1953. (AP Photo)
The smiling Queen Elizabeth framed in the window of the State coach as she left Buckingham Palace quadrangle for Westminster Abbey for the Coronation ceremony on June 2, 1953 in London. (AP Photo/pool)
Britain's Queen Elizabeth II holds Prince Charles' hand as she gathers with Prince Philip, Duke of Edinburgh, and other members of the British royal family on the balcony at Buckingham Palace to greet supporters, following her coronation at Westminster Abbey. London, June. 2, 1953. Princess Anne stands next to Charles and Queen Elizabeth, the Queen Mother, second right, and Princess Margaret, right. (AP Photo/Priest)
(FILES) Britain's Queen Elizabeth II (L) accompanied by Prince Philip waves to the crowd, 02 June 1953, after being crowned solemnly at Westminter Abbey in London. Queen Elizabeth II was set Thursday 20 December 2007, to become the oldest monarch, overtaking her great-great grandmother Queen Victoria amid signs the royal family is preparing for life after 81-year-old 'Lillibet'. Victoria died in 1901 aged 81 years and 243 days, and Elizabeth will mark passing the milestone with neither pomp nor ceremony, spending the day as usual with her husband of 60 years, Prince Philip. AFP PHOTO/FILES (Photo credit should read STRINGER/AFP/Getty Images)
Queen's Guards marching along Pall Mall as part of Queen Elizabeth II's Coronation procession, London, 2nd June 1953. (Photo by Hulton Archive/Getty Images)
This view shows Britainâs New Queen Elizabeth II (third from right) and members of her party in Golden Box at Royal Opera House, Covent Garden in London on June 8, 1953, to hear first performance of a New Opera, âGloriana,â dedicated to her. At right are Queen Mother Elizabeth and the Duke of Edinburgh. On other side of Queen are Princess Margaret (left) and Norwayâs Crown Prince Olav and his wife. Opera, by composer Benjamin Britten, was especially for coronation and celebrates the triumphs of Queen Elizabeth I. (AP Photo)
Britain's Queen Elizabeth II and Prince Philip, Duke of Edinburgh, gather with other members of the British royal family to greet supporters from the balcony at Buckingham Palace, following her coronation at Westminster Abbey. London, June. 2, 1953. (AP Photo/Priest)
Queen Elizabeth II smiles at a saluting subject as she alights from her coach on arrival at Westminster Abbey, London on June 2, 1953 for her coronation. Her husband, the Duke of Edinburgh, in uniform of an Admiral of the Fleet, watches at right as maids of honor arrange the queen's train. (AP Photo)
Queen Elizabeth II, wearing the Imperial Crown, smiles and waves to crowd from balcony of Buckingham Palace on June 3, 1953 in London, on returning from Westminster Abbey following her coronation. (AP Photo)
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The BBC reported that in China, items about the queen's remarks were censored from its news bulletins.
The Chinese authorities often censor items they object to from foreign news bulletins, which can only be seen by very few people in China as foreign TV channels are only allowed in high-end hotels and a tiny number of select apartment buildings.
A spokeswoman for the queen said: "We do not comment on the queen's private conversations. However, the Chinese state visit was extremely successful and all parties worked closely to ensure it proceeded smoothly."
Xi's visit was full of pomp and ceremony, with Cameron and his finance minister George Osborne keen to impress the Chinese leader and present Britain as China's firmest friend in Europe.
The queen has been careful to keep her views to herself during her 64-year reign, but several other members of Britain's royal family have made undiplomatic comments about China in the past.
The queen's husband, Prince Philip, warned some British students in China in the 1980s that they would get "slitty eyes" if they stayed there too long.
Her eldest son, heir-to-the-throne Prince Charles, has skipped two state banquets for Chinese guests in Britain, and described some Chinese officials in a journal that was leaked to the media as "appalling old waxworks."
Relations between London and Beijing have been complicated by the weight of history, particularly the 1860 Opium War when British and French troops stole piles of plunder from the Summer Palace in the Chinese capital, then burned it to the ground.
In 2010, Cameron and a delegation of ministers caused offense during a visit to Beijing by wearing poppies - a symbol of remembrance of fallen troops for Britons, but in China a reminder of the opium trade that helped trigger the conflict.