Britain has warned it will not tolerate attempts by foreign states to intimidate or harass individuals on its soil, as it summoned China’s ambassador after two men linked to Hong Kong’s London trade office were convicted of spying on activists.

The United Kingdom’s Foreign, Commonwealth & Development Office confirmed on Saturday that Ambassador Zheng Zeguang had been summoned the previous day after the British court’s verdict in the national security case.

Bill Yuen Chung-biu, manager of the Hong Kong Economic and Trade Office in London, and Peter Wai Chi-leung, who ran a security firm, were found guilty on Thursday of assisting a foreign intelligence service.

Yuen, a retired Hong Kong police superintendent, was accused of passing surveillance requests from city authorities to Wai while working at the office.

Wai was also convicted of misconduct in public office. Evidence showed he used his position as a UK Border Force officer to obtain personal information on Hong Kong activists from official computer systems.

“It was made clear that the UK will not tolerate any attempts by foreign states to intimidate, harass or harm individuals or communities in the UK, and that such activity constitutes a serious breach of the UK’s sovereignty,” a spokesman for the Foreign Office said.