A caution may only be issued in cases where the offender has made a 'clear and reliable admission' (of his guilt) and there is a 'realistic prospect' of a conviction. In the made up example you have given, neither of these conditions are met. Indeed, the CPS won't take any case to court on one person's word against another. There are two tests that are applied before they accept a case for prosecution

I'm quite sure it isn't the decision of one "can't be d" copper, but it's been fairly well documented over a period of several years that the criminal justice system is often found wanting when it comes to how they deal with sex crimes and victims of sex crimes.

I'm not some hysterical Daily Mail reader looking for something to feel outraged about, and I have genuinely considered a range of potential circumstances where this course of action may be appropriate. I just can't for the life of me think of a situation where a person has admitted rape, where there is evidence that they have committed rape, and it's appropriate to administer a police caution.

That may be true but equally it might not be the reason. We don't know but either way that doesn't make any difference to the fact serious crimes are resulting in cautions but the Hulme case was like the trial of the century. The cautions also relate to other offences such as drug dealing which don't need a victim for prosecution to take place in any case.

I like everyone on here do not know the ins and outs of why there are cautions for rape. What I would say though is that the police, CPS, social services, victims and guardians are all consulted in the process when required. I like most can't think of many reasons why you would be cautioned for rape. But at the risk of wording this wrongly I would throw in two possibles.
The teenage boy who thinks his girlfriend is over the age of consent. There are many examples of this. Is that rape? Well if she is under 13 yes, but there is a grey area from 13 to 16 depending I would say on the age of the suspect. I have no examples to share but I would imagine its hard to make the right decision in these cases.
Also think of adults with mental ages of children. They have sex. Is she of the correct mental ability to consent? I don't know enough to be able to say, but I am sure that would be a tough call.
I could be way off the mark here, but sadly its not as black and white as the press seem to think.

Going back to Pryce and Huhne. I fail to see what holding them any longer will serve to do. They have done 8 weeks I believe. That's a full 8 weeks more than I could ever do. They will not reoffend for that I am certain. Their lives as they knew them are ruined. Lets move on.
As for trial of the century as I think it was referred. That's the press for you not the criminal justice system. Within court they were treated in exactly the same way as anyone else.

The m,an's admittedly a Tory scumbag toilet, but Grayling explained that

Consensual sex with a person between the ages of 13 and 16 is not classed as rape.

I can see that point, but I then begin to wonder why a perpetrator would confess to rape if the victim was unwilling to appear in court. If the case rests on the victim's testimony and the defendant knows that she won't testify, why cough to it?