The long arm of the law is one thing. The long duration of the law is another. It is a year since the police investigation into the cash-for-honours saga began after a complaint was received from a Scottish Nationalist MP. In the early days of the inquiry, Assistant Commissioner John Yates pledged that his team would be “focused and proportionate” as they dealt with this matter. Yet, as we report today, the final file, once expected in July last year, then September, then December, then January, until very recently next week, may not be submitted until next month at the earliest. At this rate, the Crown Prosecution Service will not be in a position to make a decision on charges until after Tony Blair has departed Downing Street. And even the timing of that event has become dependent on when the police finally announce that their business is finished.

In large part, delays have occurred because the character and content of the investigation have evolved, if not mutated. This murky affair began with the accusation that those who offered to make large donations to the city academy initiative much cherished by the Prime Minister could expect political honours in return for their contributions. That line of inquiry has closed. It then moved on to look at whether the loans that the Labour Party (and the Conservatives) recklessly chose to solicit instead of donations before the last general election were the conduit for an improper and illegal trade in titles. It seems that there is insufficient material for the police to proceed further here, too. The spotlight has thus switched to whether those in Mr Blair’s circle broke the law by seeking to “cover up” acts that of themselves were probably not criminal.

In truth, no one involved in this investigation emerges well from it. Mr Blair made a huge ethical error in deciding to evade the spirit, if not the letter, of legislation that he had introduced, which was intended to make plain who was providing financial backing to the political parties and what, if anything, they may have obtained in return. The police have been heavy-handed in their treatment of certain Downing Street staff and have been no more subtle in asking the Attorney-General to impose injunctions against the media (which have now, in effect, been withdrawn) to block what is a standard method of reporting evidence before charges are laid.

The stakes have become so high that there is the risk that the police will feel obliged to push as hard as they can for such charges, or else their endeavours will be dismissed as a farce. If this inquiry ended tomorrow and nothing more happened, it would still have had a significant impact on public life. The loans loophole has been closed. The rules relating to party funding are under review and there will almost certainly be changes to limit the influence of big donors and donations. When the House of Commons debates the composition of the House of Lords today, it is more likely to back an elected element for the second chamber because past practices of creating life peerages have been exposed as unsatisfactory. If there was an informal and unstated culture of exchanging cheques for ermine it has been ended.

The police need to recognise that they should bring their work to a conclusion as soon as possible. If this requires extra resources, then these should be allocated. This was always a strange investigation, operating deep in the no man’s land between the law and politics. It is time for the rival armies to return to their respective trenches.