Last year the defendant in a Swansea rape trial was acquitted because the prosecution admitted it could not prove that the alleged victim had withheld her consent for sex. She had been drunk, and the judge directed the jury to return a verdict of not guilty. If this were an isolated case it would be, at best, unfortunate for all concerned; at worst, a grave miscarriage of justice. But it is not isolated. Barely 5 per cent of rape allegations result in convictions. A minority of such allegations may be groundless or weak, but most are not. According to the British Crime Survey they represent just 15 per cent of all rapes, most of which still go entirely unreported.

The first figure reflects a shameful failure of the criminal justice system. The second amounts to a social tragedy visited on nearly 100,000 women a year, in many cases scarring them for life. Both were cited in yesterday’s consultation paper on the law on rape signed by Mike O’Brien, the Solicitor-General, who noted with breathtaking understatement that “an awful lot of people who are committing rapes are getting away with it”.

If the crime at issue were murder, British justice would now be in the dock. The crime of rape damages its victims in less final but more complex ways and is necessarily harder to prosecute. Cases can hinge on the defendant’s word against the accuser’s. Scientific and circumstantial evidence is vital but easily lost, and delays between a rape being committed and reported can stretch to years. None of this gives the links in the prosecutorial chain a licence to give up on rape, yet they have come close to doing so.

The weakest links are the earliest. Despite decades of investment in specialist sex crimes units, the nation’s police forces still fail to refer up to two thirds of reported rapes to the Crown Prosecution Service. In half these cases the alleged victims withdraw from what is inevitably a traumatic process before referral. In the other half, police decide that their cases will not stand up in court — and half of those that do reach the trial stage end in acquittal.

The Government has already amended the law on rape by redefining “consent”, in the Sexual Offences Act 2003, as agreement by free choice rather than the absence of a refusal. It is too soon to judge properly what difference if any this has made to conviction rates. But it is not too soon to review what is clearly a failing system. Sweeping social change over the past two generations has unquestionably emboldened women in ways that expose them more than ever to danger from potential rapists — whether as much-maligned “ladettes” or simply enjoying their right to stay out late. The law must now catch up.

Yesterday’s calls for videotaped police interviews to be admitted in court, for gentler handling of accusers under cross-examination and for more resources to support them during the prosecution process should all be welcomed. Testifying by videolink, as is already allowed for minors, should also be considered. And it may be time to clarify the legal definition of “capa-city” to give consent for sex, though in the end no law can define what level of inebriation precludes meaningful consent. That is for juries to decide.

Women must know that no culture of disbelief will thwart them if they claim to have been raped. And rapists must know that, if reported, they will be tried and sentenced. Justice demands nothing less.