A little reading will show why many victims didn't say anything at the time as well as many who did speak up and were ignored.

Victims reporting assaults can offer corroboration regarding the offences - modus operandi is often used as evidence in all sorts of crimes.

After many years there is unlikely to be any hard evidence, although there was in one of the cases against RH - there is no need for physical evidence to secure a conviction, there simply has to be a case where sufficient evidence can be put before a jury to convince them beyond a reasonable doubt that the accused is guilty.

R ape is probably one of the hardest crimes to prove as is shown by the number of convictions compared to the number of reports - does that mean that future reports shouldn't be taken seriously and vigorously investigated?  I would hope that you'd agree they should.  

Exactly the same can be said of historic complaints - they should be treated seriously and the claims should be investigated and where the CPS believes there is a reasonable likelihood of 'success' court proceedings should commence.