The case against a former Royal Marine found dead after being accused of assisting the Hong Kong intelligence service has been formally closed.

Matthew Trickett, 37, an immigration enforcement officer and private investigator from Maidenhead, Berkshire, was one of three men charged with offences under the National Security Act.

He had appeared at Westminster Magistrates’ Court alongside co-defendants Chi (Peter) Leung Wai, and Chung Biu Yuen, on May 13.

At that hearing, the prosecution had asked for Mr Trickett to be remanded in custody for his own welfare ahead of his next hearing at the Old Bailey.

However, he was granted bail and on May 19, Mr Trickett was found dead in Grenfell Park, Maidenhead, after a report from a member of the public.

At a hearing at the Old Bailey on Friday, prosecutor Alistair Richardson said the Crown Prosecution had notified the court that the case against Trickett would be formally “discontinued”.

He said: “As has widely been reported, Matthew Trickett died on May 19 this year. The cause of his death is currently given as unexplained. His death has been confirmed by the coroner.”

He also asked for the formal revocation of Mr Trickett’s electronic tag.

At the same hearing, Mr Justice Jeremy Baker set a timetable for the case against the two co-defendants.

Chi (Peter) Leung Wai, 38, from Staines, Surrey; and Chung Biu Yuen, 63, from Hackney, east London, spoke only to confirm their identities.

A provisional five-week trial was set for Kingston Crown Court from February 10 2024.

A further hearing at the Old Bailey will take place on October 25.

Mr Justice Baker confirmed the case would be heard by a High Court judge and granted the two men continued conditional bail.

The defendants were all charged under the National Security Act after an investigation by the Metropolitan Police Counter Terrorism Command.

The charges alleged that between December 20 2023 and May 2 2024, Yuen, Wai and Mr Trickett agreed to undertake information gathering, surveillance and acts of deception that were likely to materially assist a foreign intelligence service.

It is also alleged that on May 1 they forced entry into a UK residential address, being reckless as to whether the prohibited conduct, or course of conduct of which it forms part, would have an interference effect.

Thames Valley Police had referred itself to the Independent Office for Police Conduct (IOPC) because Mr Trickett’s bail condition required him to regularly register at a police station.

The Independent Office for Police Conduct had assessed that referral and decided the matter should be investigated by TVP’s professional standards department.

Mr Trickett was formerly employed by the UK Border Force at Heathrow Airport, before joining Home Office Immigration Enforcement on February 21 2024.

He was also the director of MTR Consultancy, a security firm formed in April 2021.