The duty of prosecution is usually irksome, inconvenient and burthensome,” said the Criminal Law Commission in 1845 as it recommended the creation of a new legal office to take on the function previously the responsibility of the injured party. It was not until 1880 that the first Director of Public Prosecutions (DPP) took up the post; and few incumbents since would disagree with the commission’s lugubrious assessment of the role. The latest, Alison Saunders, has announced that she will not seek a further term in office when it expires later this year; and ministers had indicated that it would not be renewed in any case.

The DPP has often been the whipping boy for failings in the criminal justice...