Earlier this year, after Helensburgh man William Rigby admitted carrying out horrific sexual assaults on three young victims, I spoke to a teenager who told me that she, too, had been abused by the same man seven years ago.

She told me then that she had initially tried to forget about it, and had gone to the police only after listening to a talk at her school about sexual abuse, but that nothing more happened until further allegations were made last year that Rigby had abused other children.

That girl, who is now aged 17, told me then that she felt let down by the justice system after Rigby admitted every other charge against him, but pleaded not guilty to the one in which she was the alleged victim – a plea that was, in words that are uttered every day in courts across the land, deemed to be “acceptable to the Crown”.

READ MORE: Helensburgh rapist admits six charges of sexual abuse against children

As reported on our website today, her view has not changed now that Rigby has been sentenced on the six charges to which he pleaded guilty. And her feeling that she has not been believed, despite doing exactly what the police and other authorities say people who have been abused should do, is entirely understandable.

Part of the answer to why the Crown accepts ‘not guilty’ pleas will, in many cases, lie in the question of whether the Crown thinks it can prove the accused is guilty. And I can only assume that, based on the information available at the time, the Crown did not think it could prove Rigby was guilty of seven charges rather than six.

How much effort was put in to considering what would be required to prove his guilt on that seventh charge? I hope the answer is is “every effort”.

READ MORE: William Rigby 'could have been stopped – but no-one listened to me'

I do know that allegations of sexual abuse are extremely difficult to prove, and that doing so can have a harrowing impact on everyone involved. And I really, really hope that someone, somewhere, has not thought “six guilty pleas from seven charges – that’s not a bad result, we’ll take that”.

As has been shown in the recent Carl Beech case, where a man who made all sorts of lurid accusations against well known public figures over a number of years, which were later found to be entirely false, was jailed for 18 years, there are grave dangers in the authorities’ default position of all abuse allegations being true.

But the consequences of victims of abuse being put off going to the authorities because they think they won’t be believed are surely just as serious.

READ MORE: Police admit shock at scale of Helensburgh man William Rigby's abuse of children

Much work has been done in the last decade or so to encourage people to come forward and report abuse – but that work, it seems, is far from complete.