For many of us who work in the criminal courts, Sir Ken Macdonald’s words that we “intend to do more for ourselves” gave greater cause for anxiety about the independence of the prosecution than for applause. Such anxiety was fuelled when on the same day the article was published the case against two men in Lancashire Constabulary’s biggest murder investigation collapsed.

Last summer the defendants faced a long trial. After nine days in retirement, the jury failed to agree. The retrial was to proceed on the same evidence on which the Crown had sought convictions last year; but material in the possession of the prosecution that should have been disclosed long before the first trial showed that it never had a case. The defendants spent two and a half years in custody. One, Mohammed Raveshi, was the longest-serving remand prisoner in the 200-year history of Preston prison.

In November 2003 a 14-year-old Blackpool girl disappeared. Thirteen months later, acting on hearsay, which was little better than gossip, the police targeted the defendants, both of whom had lived in Britain many years.

In February 2005 Raveshi’s house was bugged. Digital audio tapes (DATs) were produced, containing passages later relied on by the Crown; the passages were obscure and difficult to hear. A detective sergeant of Blackpool police, who was intimately involved in the investigation, transcribed the conversations. These were used at the first trial in spite of strong advice from the prosecution’s expert about the dangers of bias. He advised against using transcripts prepared by someone “with no specialist knowledge of phonetics, but with considerable knowledge of the case which inevitably influences judgments regarding the recordings”. Four other experts agreed with him.

The Crown Prosecution Service (CPS) pressed on regardless. The recordings were so difficult that five experts failed to achieve an agreed version, but the detective sergeant claimed to hear the first defendant admit to killing the girl and Raveshi admit to cutting up the body and putting it through a mincing machine in their kebab shop. In fact they were talking about tiling the shop and, despite days of examination of various premises connected to the defendants, no evidence was found to support the claims — not even a mincing machine.

Despite defence objections, the judge admitted this evidence at the first trial; neither he nor the defence were told that VHS equipment, monitoring Raveshi’s house, contained soundtrack that was clearer than the DATs and cast doubt on the transcriptions. Defence requests for copies of the VHS tapes were rejected by the CPS, who said they were “irrelevant” and “clearly not disclosable”. It was only many months after the first trial that we discovered audio on the VHS.

The other plank of the prosecution case was a witness who gave hearsay evidence about being told by the first defendant’s brother that the men had murdered the girl and cut up her body. Again, neither judge nor defence was informed that this evidence was undermined, this time by covert tape recordings of conversations between the witness and the brother. Those tapes were not disclosed until two weeks before the retrial.

When these disclosure failures emerged (two among many) the prosecution threw in the towel. But it was not “greater efficiency and improved performance” by the CPS that provoked this surrender. The police and the CPS sought an adjournment and wanted to begin again. Left to them a grave miscarriage of justice might have been perpetrated. What led to the collapse was the advice and decisions of the QC and junior, instructed by the CPS but both barristers in private practice, who brought to their work the key quality of independence.

The independence of the Bar is vital to the fair prosecution of criminal cases. That independence is a virtue that cannot be replicated within a government department whose employees rely on it for their livelihood. They inevitably have a prosecution perspective.

Leaving aside the question of cost (and cost comparisons between CPS lawyers and barristers reveal little difference) “getting it right more often than we used to”, as the DPP put it, is complacent, displays a paucity of ambition and is cold comfort to defendants spending years on remand for offences they did not commit.

If independence is removed from the prosecution process, the dreadful failures we saw in this case will become more frequent.

The author, a QC, is at Deans Court Chambers, Manchester, and 3 Paper Buildings

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