Mackey was a veteran of the courts, handling cases of gangland murder and major drug busts — and though he sometimes disliked the verdicts juries came to, he accepted them. But this case was different. “Something went wrong here,” he said. “Something went very, very wrong.”

Studying the case papers, it was impossible to see how the case at Chester crown court could have been proved beyond reasonable doubt. (For two jurors it was not and Sally Clark was convicted by a majority verdict.).

The following week The Sunday Times ran a story questioning the safety of her conviction. It was the start of a three-year campaign that ended last Wednesday afternoon when her conviction was quashed by the Court of Appeal.

It was an emotional moment, watching her walk free at last from the cells to the front steps of the Royal Courts of Justice, wearing trousers that were too short for her and with a jagged prison haircut framing her pale, determined face.

There were no smiles and no tears. “There are no winners here,” she said. “We have all lost out.” There was no party or celebration. Sally was determined nobody should forget that at the centre of this case were two dead babies for whom she and her husband, Steve, had never been able to properly grieve.

After three years in jail, Sally’s team of supporters was finally able to prove she was innocent, exposing the bankruptcy of a prosecution case based on the theory that more than one cot death in any family is an automatic cause for suspicion.

Christopher, the Clarks’ first son, died in December 1996 and the cause of death was originally certified as respiratory infection. We now know that the overwhelming probability is that Harry, the baby they lost two years later, also died a natural death from a bacterial infection.

Tests showing that his body was riddled with staphylococcus aureus were withheld from the jury and were only unearthed last autumn when Steve was finally able to wrest all the boy’s medical notes from Macclesfield general hospital. Even he did not immediately appreciate their importance.

“I was puzzled because we believed the microbiological tests were negative,” he said. “I showed them to one of our experts and he basically said ‘Eureka!’.”

The tests, buried in the wrong file, were commissioned by Dr Alan Williams, the Home Office pathologist who carried out post-mortem examinations on both boys. When he was invited last week by the Appeal Court judges to explain himself, he declined.

The case over, all Sally wanted to do, understandably, was to go home, relax and wallow in a long, hot bath. In other words, to start living again. But after all she has been through, that won’t be easy.

FRANK LOCKYER, Sally’s father who, like her husband, has been a source of unwavering support, sent her a “fatherly letter” during her last weeks in prison, warning her that she would have to take time to get used to being with Steve again.

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