A British man who was charged with spying for China has told the BBC he was a "convenient fall guy" for UK police and security services who wanted to put espionage threats by foreign states "on the map".
Chris Cash, a former parliamentary researcher, has shared more than 6,000 messages with us revealing how a Chinese official sought information about sensitive political matters in the UK - including the 2022 Tory leadership battle to decide the next prime minister.
The messages show how Cash's friend in China, Chris Berry - with whom he had been sharing information - dramatically described a "secret" meeting between Berry and a high-ranking Chinese official.
Berry said he had been told that China was concerned about how a British MP it had sanctioned might be promoted to a cabinet role.
The messages also reveal how Cash used his friend as a reference during vetting for a parliamentary pass - which was approved.
In his first interview since his acquittal, which sparked a political row over the government's failure to designate China as a "threat", Cash says he would "never do anything" to harm UK national security.
But he admits he was "unprofessional and naive" to send "gossiping" texts to his friend, whom he met in 2018 when they both taught English in a school in China.
Although the trove of messages shows him discussing sensitive topics, there is no evidence in them that Cash was paid by, or sympathetic to, the Chinese Communist Party.
With the government having previously said that Chinese spies were targeting UK officials across the political, defence and business sectors with increasingly sophisticated espionage operations, Cash believes his case was pursued as a warning to others.
Berry declined to comment on this story, but at the time of his acquittal said he denied any wrongdoing and that he had been "unfairly subjected to a trial by media".
He said he had provided reports to a Chinese company, which he believed had clients seeking to develop trading links with the UK, and those reports contained no classified information and relied on public sources.
Cash returned to the UK in 2019, saying in his resignation message for his job in China that he felt "guilty sitting back and participating in a system that I am uncomfortable with".
He later became the director of a small policy group run by China-sceptic Conservative MPs in Westminster.
Meanwhile, Berry stayed in China writing reports for a large consultancy which, like many Chinese companies, has links to the government.
Whether Berry correctly identified his host remains unclear. He has since disputed the suggestion that he met someone as senior as Cai Qi.
What is beyond dispute is that he believed he may have met someone highly placed within the Chinese political system.
For Chris Cash, this unusual encounter did not prompt alarm bells. Asked why not, Cash tells the BBC: "Because I didn't think anything of the meeting, really."
We ask Cash why his friend might have been asked to such a meeting. "Strange things happen in China... you know we would often brush shoulders with sort of quite senior members of the Chinese communist party," he tells us.
Challenged about whether he had read the Wikipedia link at the time, Cash says he had "skimmed it", adding that it described him as a judge and a provincial-level official. "I just thought it was a weird meeting with a guy who'd taken an interest," he says.
Six months later, Berry said in text messages that "off the record" he had it "on pretty good authority" that China was considering dropping sanctions against Tom Tugendhat, one of the Conservative MPs in the China Research Group, where Cash worked.
Berry wrote that this would happen as long as the West "continued to show signals that they are willing to work together".
The Chinese believed it would be "extremely embarrassing" if Tugendhat became prime minister or foreign secretary while under Chinese sanctions, Berry said.
At the time of the meeting in summer 2022, China-sceptic Tugendhat was seen as a possible contender to succeed Boris Johnson, or become UK foreign secretary.
He was actually appointed as security minister by Liz Truss, and Beijing lifted sanctions on him in January 2026.
His laptop and phone were taken - this may have enabled his Signal chats to be downloaded.
Berry later messaged Cash about it.
Cash says he had not been alarmed by this: "I thought it was just standard... for a guy who'd been in China."
As the investigation progressed, it became clear the authorities believed Cash and Berry had been involved in an informal, but dangerous, exchange of information that was "prejudicial to the safety and interests of the UK".
The allegations were based on 6,273 messages between the pair - the same ones Cash has now shared with the BBC. Cash's solicitor has told the BBC they are genuine.
They cover a period when Cash had joined the China Research Group (CRG), founded by Tugendhat and fellow Tory MP Alicia Kearns, and when Berry was working for a Chinese company called Strong, where part of his work involved writing political and economic reports for clients.
According to court documents, Berry was said to have compiled 34 reports for a man linked to the Chinese state spy agency, relaying information passed on to him by Cash. Strong did not respond to the BBC's request for comment.
The CRG's office was across the Thames from Westminster, but Cash regularly had meetings in Parliament. Cash did not have government security clearance and there is no evidence he had access to classified documents.
Despite being thousands of miles apart, the two friends remained in close contact, often messaging daily.
The messages reviewed by the BBC show them discussing topics including sanctions on China, the tech company Huawei, human rights, Hong Kong, Taiwan and British foreign policy.
Cash says he used the Signal app for almost all his contacts with people in China - "more for their protection" - as he says discussing the government "could land someone… in trouble". He and Berry did not use the app's "disappearing messages" function.
Much of the information they discussed was publicly available, says Cash - who has given the BBC a detailed spreadsheet with links and references in an attempt to prove it.
But sometimes he did share with Berry his impressions from meetings and private discussions in Westminster. On 12 occasions in the messages, he labelled information "off the record" or "very off the record" before passing it on.
Cash says this was "just me excitedly sharing things that I was doing with him at work".
One message recounted views allegedly expressed in private by Britain's then-ambassador to China, Dame Caroline Wilson, during a discussion with the CRG about its work on China's influence on UK universities.
Cash also messaged Berry sharing unverified rumours about the sex lives of two UK cabinet ministers. There is no evidence Berry passed this to his Chinese colleagues.
Cash says he regarded such exchanges as routine political discussion. "We weren't working with classified information," he says.
At every previous court appearance he had been mobbed, but the press had not been informed about this hearing.
Eventually his team found a lone BBC journalist. "I said my piece outside the Old Bailey. And that was a real high point. I felt that I could start to move on with my life."
It wouldn't be that simple.
Across the city, House of Commons Speaker Lindsay Hoyle was seething. "It is this Parliament that has been spied on," he declared. "It is MPs' offices that have been infiltrated."
There would be days of political debate and a raucous prime minister's questions where Tory leader Kemi Badenoch would claim: "This all stinks of a cover-up."
"I'd been acquitted by law, but then I was traduced in Parliament," Cash says. "It was almost like I was convicted in the court of public opinion again, by people who I had worked with and trusted and that felt horrible."
Today Cash's life is almost unrecognisable. He has lost his dream job, his relationship, and his closest friend from university.
"We talked about being each other's best men," Cash says. Instead, when the friend got married last year, Cash was not even invited.
He is also no longer in contact with Berry.
"I've been applying for basic admin jobs and having trouble recently," Cash says.
"I'm angry and upset with how everything played out, and I do feel let down."
But when asked, Cash stops short of saying he feels Berry betrayed him. Does he think his friend was spying for the Chinese government?
"He would have to have his time in court to defend himself," Cash answers. "I think it'd be wrong of me to speculate and hypocritical given the speculation that I've been subject to. But we're no longer friends."
Berry declined to comment on this story, but at the time of his acquittal said his reports "concerned economic and commercial issues widely discussed in the UK at the time and drew on information freely in the public domain".
Like his former friend, Chris Cash is innocent in the eyes of the law, but his reputation has undoubtedly been trashed.
Many in Parliament still think they were spies. And with more of the messages between these former friends now revealed, the debate over their actions could be reignited.
"It was a gruelling ordeal," Cash says. "But I'm a fundamentally positive person… I'm positive about what the future holds."
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