Queen Elizabeth was caught making a gaffe about a "rude" Chinese delegation soon after British Prime Minister David Cameron called Nigeria and Afghanistan "possibly the two most corrupt countries in the world" in inadvertently public remarks on Tuesday.
At a garden party event, the queen was caught on camera describing the delegation for a Chinese state visit last year as "rude".
Police commander Lucy D'Orsi was introduced to the queen as the woman who oversaw security for the visit of President Xi Jinping and his wife in October, to which the monarch replied: "Oh, bad luck".
D'Orsi was recorded as saying, "I'm not sure whether you knew, but it was quite a testing time for me," to which the queen replied that she did know, before adding that members of the Chinese delegation "were very rude to the ambassador".
The police commander agreed, saying, "It was very rude and very undiplomatic I thought". It was not clear which members of the delegation they were referring to.
Beijing and mainland state media at the time hailed the visit as a high watermark in Sino-British relations.
Earlier British Prime Minister David Cameron was caught on microphone Tuesday saying that leaders of "fantastically corrupt" countries including Nigeria and Afghanistan will attend an anti-corruption summit in London this week.
At a Buckingham Palace reception with Queen Elizabeth II, a television microphone caught Cameron saying "we have got some leaders of some fantastically corrupt countries coming to Britain.
He referred to "Nigeria and Afghanistan - possibly two of the most corrupt countries in the world."
A Downing Street spokeswoman said it would not comment on a private conversation, but noted that both Buhari and Ghani "have acknowledged the scale of the corruption challenge they face in their countries".