"...they only HAVE to show all three if it is challenged"
Of course. However, any police force facing regular successful challenges is likely to have its policies scrutinised. The fact is, Peter, that you and I will not agree on matters such as this. I believe it is important for a robust system of checks to be in place (either that or no system at all so that we all know where we stand). It must be properly scrutinised by the courts if challenged (as in this case). You clearly do not believe that.
There is no doubt that many, many people who have committed crimes remain unconvicted either because they are never prosecuted or the prosecution fails. "Better that a hundred guilty men are freed rather than one innocent man convicted" etc. That's fine as far as the criminal justice system is concerned. The bar to a successful prosecution is necessarily set very high. But this is about protecting children and vulnerable adults and the bar is quite rightly very much lower.