A London court has heard that a young mother unwittingly became entangled in what prosecutors describe as a covert surveillance effort linked to Hong Kong authorities, as testimony continues in a high-profile national security trial in the United Kingdom.

The case is being heard at the Central Criminal Court, commonly known as the Old Bailey, where two men stand accused of assisting a foreign intelligence service by conducting what prosecutors call a “shadow policing” operation in Britain.

The defendants, former Hong Kong police officer Chung Biu Yuen and former UK Border Force official Chi Leung “Peter” Wai, deny the charges.

According to prosecutors, the pair allegedly carried out surveillance, intelligence gathering and deceptive tactics between late 2023 and mid-2024 targeting individuals viewed by Hong Kong authorities as persons of interest, including activists and members of the diaspora living in the United Kingdom.

The alleged activities are said to have included monitoring protests, compiling reports on individuals and attempting to gain access to private residences.

During the trial, jurors heard evidence about a young mother who prosecutors said had little understanding of the broader operation that she had become connected to.

Defence lawyers argued that she had been unaware of what one witness described as the “tentacles” of a wider intelligence-gathering effort reaching from Hong Kong into the United Kingdom.

Prosecutors allege that the defendants acted as an unofficial extension of Hong Kong law-enforcement authority, collecting information and conducting surveillance activities on British soil.

Authorities say the work coincided with broader efforts by Hong Kong police to monitor overseas activists and individuals accused of national security offences.

Yuen, who previously served as a superintendent in the Hong Kong police and later worked at the Hong Kong Economic and Trade Office in London, is accused of directing elements of the operation.

Wai, who had worked as a Border Force officer and volunteer police constable, is alleged to have used access to official databases and private security networks to assist with intelligence gathering.

The prosecution further alleges that deceptive tactics were used in attempts to obtain information or gain entry to a property linked to one of the individuals under surveillance.

Both defendants have pleaded not guilty to charges brought under Britain’s National Security Act, which criminalises assisting foreign intelligence services and foreign interference in the country’s political and civic life.

The trial, which opened in early March, is expected to last several weeks and is being closely watched by legal observers and policymakers because it is among the first cases brought under the United Kingdom’s new national security legislation.

Proceedings are continuing as the court examines evidence about how the alleged operation was organised and whether those involved fully understood the nature of the activities taking place.