Allegations that two suspected Chinese spies were working in Britain's parliament sent shock waves around Westminster and the United Kingdom after the men's arrest in 2023.
That shock morphed into surprise and scrutiny, after charges against the pair were sensationally dropped last month.
The British government has come under sustained criticism since the case collapsed, with critics saying the Starmer government is worried about upsetting China.
Here's what the case is about and why it has proved controversial.
What is the UK Chinese spying case?
Christopher Cash, a former director of the China Research Group think-tank, and Christopher Berry, who was a researcher for a senior MP, were arrested by British police in March 2023 on suspicion of spying for China.
The men were charged with an offence under the 1911 Official Secrets Act (OSA) in April 2024, after allegedly passing politically sensitive information to a Chinese intelligence agent known as "Alex".
Both have denied any wrongdoing, and China has always maintained the case was entirely fabricated and a malicious slander.
In an unexpected move, Britain's Crown Prosecution Service (CPS) dropped the charges on September 15, a month before the trial was due to start.
It said the case no longer met the evidential threshold.
Why did the spying case collapse?
Since the case was dropped, UK Prime Minister Keir Starmer's Labour government has been accused by the Conservative Party of undermining the prosecution in order to avoid upsetting China, with which it is seeking better economic ties.
Opposition leader Kemi Badenoch told UK parliament on Wednesday that the collapse was "unbelievable", adding that it "all stinks of a cover up".
She blamed the collapse on government ministers who were "too weak to stand up to China".
Critics have particularly singled out Britain's National Security Adviser Jonathan Powell because of what they say are his ties to China.
The UK Labour government has rejected these accusations, saying Mr Powell played no role in deciding the content of the evidence.
"Suggestions that the government concealed evidence, withdrew witnesses, or restricted the ability of witnesses to draw on particular bits of evidence are all untrue," UK Security Minister Dan Jarvis said in his statement to the House of Commons.
Sir Keir said the decision to drop the case was made independently by the CPS and that ministers were disappointed it had not gone ahead.
He also denied claims, pushed by the Conservative Party, now in opposition, that officials privately lobbied for the charges to be dropped over fears a prosecution could prompt China to pull its investment in the UK.
However, the CPS said that prior to the prosecution being dropped, it had repeatedly asked the government for new evidence that it believed was necessary for the case to go ahead.
What is at the centre of the case?
Two words are key to the issue.
Under the OSA, a law brought in to deal with German spying before World War I, it is an offence to communicate documents which might be useful to "an enemy".
At the time when the men were charged, Britain's then-Conservative government had classified China as an "epoch-defining challenge" but stopped short of officially labelling it a threat.
However, politicians and the intelligence agencies had regularly warned about the threat of Chinese espionage and activities designed to influence British politicians, businesses and academia.
In July 2024, in a separate case which involved a team of Bulgarians later found guilty of spying for Russia, London's Court of Appeal determined that an enemy under the OSA meant a country which "represents a current threat to the national security of the UK".
Following that ruling, the CPS said it had sought new evidence from the government, but that none of the additional witness statements obtained stated that China was a threat to national security at the time of the offence.
The government said the statements, provided by a deputy national security adviser without any involvement from Mr Powell, had to state the official position at the time of the charge under the then Conservative administration.
The CPS said it was now up to the government whether to make those statements public.
On Wednesday, Sir Keir said they would be released.
"The case did not proceed because the policy of the past government did not meet the test that was necessary, that is the long and the short of it," he told parliament.
"Far from evading I have said I will disclose the full witness statements ... and the allegation that somehow they were changed, that the first statement, the second statements are different, is completely and utterly unfounded."
Will the release make any difference?
It is possible that even disclosing these statements will fail to provide clarity on who was right, as some legal experts suggest both the government and the CPS got themselves in a muddle over the issue.
The experts said that if the CPS had enough evidence to bring a charge in April 2024, then it was not clear what more they needed after the Court of Appeal's ruling which, if anything, made it easier to define an "enemy" under the OSA.
However, that is unlikely to deflect criticism that the government appeared to be unwilling to provide evidence that made clear China was a threat, even if it was not officially described as such, because it would have meant stating it publicly in court.
The UK government said that the OSA had been replaced by the 2023 National Security Act, which Mr Jarvis said closed "the loopholes that have been exposed by this particular case".
Reuters/ABC
