It was a hot, early summer day in 2006 when the body of a frail, reclusive pensioner who had lived alone in a tumbledown house in one of Hampstead's most expensive streets was found under a pile of rubbish in a back room of his home.
He had been battered to death "like a seal pup on a ice floe, with more blood than Sweeney Todd," as a barrister put it to an Old Bailey jury a year later.
He was 86-year-old Allan Chappelow, a self-published biographer of George Bernard Shaw, and he had been murdered in an attempt to steal his identity and fleece his bank accounts.
A few months after his decomposing body was discovered by police constables tipped off by bank staff who had noticed suspicious transactions in Chappelow's bank accounts, a neighbour - a Chinese dissident called Wang Yam - was standing in the pine-lined dock at the Old Bailey, charged with his murder.
Sifting through months of evidence detectives from the Metropolitan Police's Hendon murder squad had put together a compelling case for the eloquent QC Mark Ellison to present to a jury. Yam was duly found guilty and given a life sentence.
But while the case put together by the Crown pointed solely to Yam's guilt, a crucial element in his trial was missing.
For the first time in British legal history evidence heard in a murder trial was deemed to be so sensitive to national security that swathes of his defence were heard in secret.
This meant he could not receive a fair trial, his defence team argued. Now, after Yam has spent six years behind bars, the case will be reviewed by the European Court of Human Rights.
It raises important questions about our rights to an open, free trial against the state's wish to keep secret the work of its security services.
As the crown was putting together what seemed a water-tight case against Yam, using long and detailed evidence pin-pointing his motives - he was severely in debt - and movements - he could be placed via mobile phone records at various internet cafes at the same time fraud was attempted on the victim's bank accounts - alarm bells were ringing in Whitehall.
It was reported at the time that Yam was working as an MI6 informant. This speculation was stirred by then home secretary Jacqui Smith agreeing to a Public Interest Immunity Certificate, which barred the press and public from hearing huge swathes of evidence.
Yam's defence team insisted he was being framed by men "who have no allegiance to this country," a mysteriously vague allegation.
Yam's case raises disturbing questions over how our state today can use that chillingly Orwellian phrase "in the interest of national security" to override the cornerstones of what makes a society free and democratic - the due process of law being heard in open court.
Yam's story begins in 1989 with the bloody events of Tiananmen Square in Beijing. He fled to Hong Kong and asked for political asylum, saying that the Chinese authorities were trying to force him to pass on names and information about students of his - he had been a physics professor at Beijing University - who may have been involved in the protests.
Anyone with any knowledge of Britain's asylum and immigration procedures will know such a request can take time - a long, long time.
But something the physics professor said to his British contacts led him being whisked to London. Within 10 days of arriving in Britain he had the paperwork needed to start building a new life in London.
But he didn't do well here. His wife stayed in China. He did not return to teaching, but tried his hand at business with little success.
He set up a wine import company which failed, leaving him with debts of around £1.1 million, and was declared bankrupt.
He tried to change his fortunes, setting up internet domain names and then flogging them on to businesses who could use a snappy web address. It was not fruitful.
As the debts mounted, he turned to crime. The court heard how he had pretended to various estate agents in the Hampstead area he was a wealthy Hong Kong TV executive and he put in offers on houses he had no hope of ever affording, trying to use forged credit notes.
Then came the fateful day that he wandered past Chappelow's ramshackle house, with post sticking out of its small Georgian letter box.
The evidence I was allowed to hear as I sat on the Old Bailey's cramped press benches was detailed. While the idea of the life of detective in the public eye is either that of a sleuth who has some kind of sixth sense when it comes to human nature - think Morse - or a handy man to have behind the wheel of a car like Regan, in reality the compelling evidence gathered against Yam was the product of some seriously boring work. Mobile phone and computer records suggested he had masqueraded as the deceased. Witnesses identified Yam. A postman said he had taken an interest in Chappelow's post, and he was identified as using the pensioner's credit card in a curry house to pay for a dinner. It was thorough, and convincing.
In contrast, the defence did their best to pick holes - but infuriatingly, much of the evidence could not be heard in public.
Before any evidence was heard, lawyers representing national newspapers and media outlets asked for Smith's request that much of the trial be heard in secret be overturned.
Mr Justice Ouseley heard two days of evidence and decided that because the jury would be party to all that went on in court, the fact it was heard in secret was no hindrance.
He said: "The prosecution order for parts of the trail to be held in camera is stated for reasons of national security or the protection of witnesses."
The trial went ahead, with public, police and press trooping out to wait patiently in the lobby for hours at a time, wondering what sort of James Bond-style story was being told behind the court room doors.
Now, nearly five years after the trial, the European Court of Human rights in Brussels will consider whether this jeopardised Yam's right to a fair trial.
A trial heard partly in secret with the vague catch-all that it was in the interest of national security jeopardises the common law principle of open justice and also goes against the the ideals of press freedom, enshrined in European law.
The public and press are entitled to attend judicial proceedings and in criminal cases, evidence must be communicated publicly through fair and accurate court reporting. As Jeremy Bentham said: "Publicity is the very soul of justice. It is the keenest spur to exertion and the surest of all guards against improbity. It keeps the judge himself, while hearing, under trial."
Guilty or no, the trial of Yam can only remind us once again that we must be on constant guard when our government cites "national security" as a reason to ride roughshod over an individual's right to fair, open, public trial.
And regardless of Yam's rights, it is the least Allan Chappelow deserves.
The idea that if you are accused of a crime it is enshrined in our laws that you have the right to a free, open and public trial is partly the work of the 17th-century writer-revolutionary, "free born" John Lilburne.
Lilburne, a leading Leveller, participant in the Putney Debates and a radical pamphleteer, emerged as a popular hero from the battle between the despotism of monarchy and Parliament.
And when Oliver Cromwell's Parliament turned reactionary and reneged on the ideals that the common roundhead soldiers had been fighting for - values of equality before the law, fair and open trials, and their democratic rights to participate in government - he was locked up for using his quill to tell the world.
Lilburne knew all about the despotism of a rich man's legal system, having faced the death penalty for his views on four separate occasions.
He fought with both the pen and sword.
He was in the thick of it at the battles of Marston Moor and Edgehill, and also led a small battalion who saw off Prince Rupert's cavalry as they tried to take Brentford and head from the west into London.
He knew what he was fighting for. He put into writing the theory that all should be allowed a trial by their peers, to have all the evidence of the charges they are accused of put to them in public, and have the chance to answer such accusations in public, too.
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