David Cameron and Xi Jinping were locked in talks for most of Wednesday, the third day of the Chinese president's state visit.
China is investing billions in a new nuclear power plant in Somerset, while President Xi has said British-Chinese relations would be lifted to a "new height".
After talking about the effects of cheap Chinese steel on the UK's steel industry, and making it easier for Chinese businesspeople to secure UK visas, the pair headed into a joint press conference for curious journalists.
The BBC's political editor, Laura Kuenssberg, had noted beforehand that the Chinese president is usually reticent with the foreign press.
But she also managed to be the only British journalist in the room who was allowed to ask a question - and what a question it was:
President Xi: Why do you think members of the British public should be pleased to do more business with a country that is not democratic, is not transparent and has a deeply, deeply troubling attitude to human rights?
Speaking through a translator, Xi said that China places great importance on the protection of human rights but "we combine the universal value of human rights with China’s reality and we have found a part of human rights development suited to China’s national conditions".
The president did admit, however, that "there is always room for improvement."
Under President Xi's leadership more than 250 rights activists have been imprisoned, and working and prison conditions as well as medical ethics are also under scrutiny from rights groups such as Amnesty International.
Speaking on Sky News today, Chinese artist and political dissident Ai Weiwei accused David Cameron of sacrificing "essential values" for the "short term gain" of business deals.