"The court had jurisdiction to quash the conviction of a defendant who had pleaded guilty to a charge before magistrates on the basis of flawed evidence unwittingly relied on by the prosecution, even though the conviction was obtained without unfairness on the part of the court or malpractice by the prosecution. Although no dishonesty had been involved, the process leading to the convictions of the applicants for driving with excess alcohol in their blood had been corrupted by the prosecutor (a combination of the police and the Crown Prosecution Service) in a manner which was unfair in that it gave the applicants no proper opportunity to decide whether to plead guilty or not guilty and wrongly denied them a complete defence to the charges. The conduct of the prosecution therefore was analogous to fraud, collusion or perjury and entitled the court to intervene by way of judicial review."