A former Royal Marine accused of assisting the Hong Kong intelligence service has died in unexplained circumstances in a park.

Matthew Trickett, 37, an immigration enforcement officer and private investigator from Maidenhead, Berkshire, was also accused of foreign interference and had appeared at Westminster Magistrates’ Court with two other people last week.

Thames Valley Police (TVP) said Trickett was found dead in Grenfell Park, Maidenhead, at around 5.15pm on Sunday after a report from a member of the public.

An investigation is ongoing into the death, which is being treated as unexplained.

A family statement said: “We are mourning the loss of a much-loved son, brother and family member. We would be grateful if the press would respect our privacy at this difficult time and refrain from intruding on our grief.”

Trickett’s solicitor Julian Hayes, senior partner at Berris Law, said: “It has sadly been confirmed by Thames Valley Police that the body found in Grenfell Park, Maidenhead, on Sunday was that of our client Matthew Trickett.

“We are naturally shocked at this news and supporting his family as best we can.

“The death is currently being treated as unexplained by the police and further investigations are still ongoing.”

Trickett was charged along with Chi (Peter) Leung Wai, 38, from Staines, Surrey, and Chung Biu Yuen, 63, from Hackney, east London.

They were 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 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.

They had all been bailed and were due to appear at the Old Bailey on Friday.

Prosecutor Kashif Malik said during last week’s hearing that Trickett had attempted suicide after being charged, and had asked for the defendant to be remanded in custody for his own welfare.

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

The IOPC has assessed that referral and decided the matter should be investigated by TVP’s professional standards department.

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.

A police cordon was in place in Grenfell Park on Tuesday evening with several officers stationed next to a black forensics tent located close to a children’s playground.

More officers were positioned at vantage points and paths around the park.

A local resident said “there were children everywhere” in the park on Sunday when Trickett was found dead by police.

Tatiana Dioniseva, 30, told the PA news agency: “On Sunday there were so many people here – there were children everywhere.

“It was a bit bizarre because it was sunny – there were children about and then a crime scene over there.”

She said Grenfell Park, which is located close to Maidenhead railway station in Berkshire, was popular, adding: “Usually on Sundays, every bench will literally be taken.

“There are people everywhere – it’s a popular place.”