The not guilty verdicts at the recent trial of four Sun journalists on charges relating to payments to public officials has led to the Metropolitan Police’s “Operation Elveden” being branded a failure by The Sun and other tabloid newspapers. Demands to “stop the witch-hunt” and in one case a comparison between the Crown Prosecution Service and Hitler have graced our red-top press.

Yet while the many of the journalists so far tried on charges of making illegal payments to public officials have been found not guilty or face re-trials, the police inquiry into tabloid corruption has been getting results. In parallel with the well reported acquittals and hung juries of editors and reporters there have been less reported guilty verdicts, and often terms of imprisonment, for the civil servants, soldiers, police and prison officers who sold information to The Sun. A number of these cannot currently be reported for legal reasons.

One conviction we can now tell you about is that of Bettina Jordan-Barber, known as Betsy to her workmates. She was a senior and trusted Ministry of Defence (MOD) civil servant at the UK Land Forces Secretariat, responsible for welfare and disciplinary matters in the British Army. One day Mrs Jordan-Barber phoned The Sun to ask if the newspaper was planning to publish a story about an acquaintance who had been having an affair with a naval officer. She was passed on to chief reporter John Kay who, recognising her value, met her for lunch the next day where they agreed that she would tell him about important military stories in return for payment.

Over the next few years Mrs Jordan-Barber gave John Kay the basis of dozens of exclusive articles in return for payments totalling £100,000. She was ideally placed as a source as it was her job to brief the MOD press office on what lines to take if the media inquired about an incident. She would give him all the details so he could phone the press office, who would be forced to confirm them – it was perfect. It’s clear that Mrs Jordan-Barber thought of the journalist as a friend, her family called him “Godfather John” and that is how he was listed on Betsy’s mobile phone.

During his testimony at his own trial John Kay said he had assured the civil servant that “no-one in this building is ever going to betray you”. Mrs Jordan-Barber is now in prison serving a 12 month sentence for misconduct in a public office.

So how was she caught? In the wake of the phone-hacking scandal Rupert Murdoch’s News Corporation was desperate to avoid a US corporate prosecution not least because some of their senior executives were under investigation. So the company’s board agreed a “memorandum of understanding” with the police.

In return for confirmation that the company was “co-operating with the investigation” lawyers retained by the “Management Standards Committee” of News Corporation uploaded 23 million internal emails to a secure sever. The police then searched the database for words like “bung, bribe, copper, screw” and, when they came across something of interest, cross referenced it with financial records, which generally listed the name of the “confidential source” and the stories they had contributed to. This involved a lot of painstaking work but given the degree of information the police had access to it was the investigative equivalent of shooting fish in a barrel. In every trial of the public officials the prosecution produced large colour-coded timeline – documents that showed exactly who was paid how much for what; and it was all thanks to those helpful executives of the Management and Standards Committee.

It’s no surprise that most of those the sources identified pleaded guilty, especially as they would not have Britain’s biggest media organisation paying their legal bills.

The relationship between the police and the company is not what it was and the days when the media giant handed over documents with such gay abandon are over, mainly due to the Crown Prosecution Service refusing to rule out corporate charges. However that is not a lot of comfort to the confidential sources who now languish in prison.

Due to the ongoing trials and re-trials of Sun reporters there are many of these who we cannot name to avoid prejudicing future proceedings. But spare a thought for ex-Surrey PC Alan Tierney, jailed for 16 months for selling information about the arrest of footballer John Terry’s mother, or Detective Chief Inspector April Casburn who served 15 months for giving information to the News of the World about the phone-hacking investigation Neither of these cases made the front pages.

There has been much talk in the press about how the jury at The Sun four trial “stood up for free speech” which is odd because checking my notes from two months of evidence I can’t find a single reference to that phrase. There is however a more prosaic, if less newsworthy, explanation for why journalists are being acquitted and sources are not.

The Bribery Act 2010 came into force in 2012. It is now clearly an offence to pay a public official for information. The cases involving Sun journalists, however, all pre-date this, so prosecutors have been forced to rely on the old common law offence of “misconduct in a public office”. To be found guilty under this the actions of the newspaper’s source have to be “without reasonable excuse or justification” and “be so serious as to make the public lose faith in the office holder”. This is complex enough but to convict a journalist of conspiring in the offence a jury has firstly to be sure that the reporter paid the official knowing they were a public official. Secondly they must also be sure that they knew (or ought to have known) that that they had no reasonable excuse and that their actions were so serious they could constitute an offence. High hurdles to jump when all of the journalists testified that they had never heard of, or been told of, this obscure piece of law.

The one question asked by the jury in The Sun Four trial was to ask the judge to define the “so serious” part of the charge, which suggests it may have been reasonable doubt about this element of the offence, not the nebulous concept of a free press, that led to their verdicts.

Bettina Jordan-Barber was at the heart of the British establishment, married to a distinguished army officer and trusted enough to give Clarence House and Buckingham Palace confidential briefings on military matters. By all accounts PC Tierney and DCI Casburn did their jobs faithfully and well. None of them had ever come to the attention of the law until they got involved with Britain’s tabloid press, and they paid a terrible price.