Any whiff of corruption in the police is always disturbing and needs to be investigated scrupulously, lest contamination spread. This is what should have happened, and did not happen until much later, in the case of Lynette White and the South Wales Police.

Even when eight – now retired – officers stood trial last year, more than 20 years after White's murder, for perverting the course of justice by framing innocent men, the prosecution failed for want of crucial documents which were believed lost.

This week some, if not all, of those documents turned up, in the course of an inquiry by the Independent Police Complaints Commission. They were found precisely where they might have been expected to be: still in the possession of South Wales Police. Whether they had been there all along is clearly a question to be asked. But the bigger question is what should happen next. Should there, as some are pressing for, be a full public inquiry? Should the whole thing be dropped as expensive ancient history? Or should there be a retrial?

The one step that has been taken so far represents the barest minimum: the Director of Public Prosecutions, Keir Starmer, has ordered a review of how the prosecution was managed. The next priority is clearly for the rediscovered files to be examined and a judgment made about how and whether they might have affected the verdict. Preliminary reports suggest that, if the new-found documentary evidence had been available at the trial, it would have favoured the defence. That would leave the acquittal of the officers in place.

Given the many doubts surrounding this case, however, that assessment needs to be thoroughly and independently corroborated. And if there is any doubt, the case for a retrial is compelling. With the law on double jeopardy now changed, a retrial of the same men on the same charges would be possible – and preferable in almost every way, both to a public inquiry and to doing nothing. Indeed, it would be the only responsible and just course.