British Consulate Officer, Simon Cheng Man-kit, a trade and investment officer at the Hong Kong consulate’s Scottish Development International section has been detained in mainland China. 

The British Foreign and Commonwealth Office reported that Simon Cheng had attended a business event in Shenzhen, Southeast China  8th August, but had gone missing while returning to Hong Kong.

“We are extremely concerned by reports that a member of our team has been detained while returning to Hong Kong from Shenzhen. We are providing support to their family and seeking further information from authorities in Guangdong Province and Hong Kong,” said an FCO spokesperson on 20th August

Mr Cheng is a Hong Kong permanent resident who had studied in Taiwan and the UK

In a regular press conference with Geng Shuang – Deputy Director, and Foreign Ministry Spokesperson of the Ministry of Foreign Affairs of the People’s Republic of China on August 20th, when questioned on the possible detention of an employee of the British Goverment, he simply answered “I’m not aware of what you said.”
When questioned in greater depth; “According to reports, a Hong Kong resident surnamed Cheng who works in the British Consulate-General in Hong Kong went missing after he traveled to Shenzhen on August 8. According to his family, the Immigration Department of the Hong Kong SAR said that he was put under administrative detention in the mainland. Can you confirm that? Is this related to the recent protests in Hong Kong?”
Geng Shuang answered; “Like I just said, I’m not aware of what you said.”

Geng Shuang, during August 21 daily press briefing, confirmed Simon Cheng was being detailed for “public security management regulations,” he also added that the ministry had made “stern representations to Britain for the series of comments and actions they’ve made on Hong Kong,” and that the UK had been asked to “stop making these irresponsible statements, stop meddling in Hong Kong’s affairs and stop interfering in China’s internal affairs.”