A Foreign Office staff member told his girlfriend “pray for me” moments before trying to travel out of China where it is believed he is being detained.

Simon Cheng Man-kit, who works at the British Consulate-General in Hong Kong, went missing after crossing the border for a business trip on August 8.

Local media reported that Mr Cheng attended a business meeting in Shenzhen, south-eastern China, and planned to return to Hong Kong via high-speed train the same night.

However, when he failed to return to work the next day, his family, including his girlfriend Li, informed the police.

Li, who met Mr Cheng when they were both studying in the UK, told news outlet HK01 that he had contacted her shortly before the border crossing.

She shared screenshots of messages from Mr Cheng on WeChat, which is believed to be monitored by the Chinese government, as well as a conversation on WhatsApp.

“Ready to pass through the border,” one WhatsApp message read at 10.40pm. Mr Cheng added: “Pray for me.”

Mr Cheng then added in a message on WeChat: “Passing through, pray for me.”

It has also been reported by HK01 that he told colleagues during the business trip to delete WeChat before they crossed the border back into Hong Kong.

Hong Kong Protests
Mass pro-democracy demonstrations have become a regular weekend activity in Hong Kong (Vincent Yu/AP)

Mr Cheng’s disappearance comes after weeks of pro-democracy protests sparked by a now-suspended bill that would have allowed extraditions from Hong Kong into China.

Tensions remain high as mass demonstrations continue with protesters criticising both the Hong Kong and Chinese governments.

Hong Kong authorities confirmed he had not been arrested in the territory before it was discovered he had been detained in China.

It is believed that, although he works for Scottish Development International, Mr Cheng is employed by the British Consulate-General in Hong Kong.

Mr Cheng is a Hong Kong permanent resident who had studied in the UK and Taiwan, but it is not known if he used any diplomatic documents for the crossing.

A Foreign and Commonwealth Office spokesman said: “We are 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.”

The Scottish Government said it was concerned for Mr Cheng’s welfare and was liaising with the Foreign Office.

A spokesman added: “We are aware of this incident and we are concerned for Mr Cheng’s welfare.

“We are liaising with the FCO, who are in contact with Mr Cheng’s family, the authorities in Guangzhou and Hong Kong, and are seeking further information.”