Sorry, but all this talk of "values" and "they should have known what to expect" etc is bullshit.
I am sure some of the women attending knew what this type of event was like. Many did not or if they had an inkling, did not expect it to be as bad as it was.
If I was 19, looking for extra money waitressing etc, there is NO WAY I would assume that serving drinks at a charity event at a prestigious, respectable hotel for £15 an hour would involve "extras". They may have twigged that they were effectively being paid to look pretty, but I don't think they were given any reason to suspect what went on at that event.
I would probably feel quite excited about it - a posh black tie do at glamorous location with the famous and powerful. Imagine expecting that, and then the growing realisation of what you have actually signed up for....
They ask you to wear black underwear? Well, maybe there's UV lighting, or they've had problems in the past with girls showing up with bright pink bra straps on show... it is a charity event at a respectable, posh hotel.
They give all the women skimpy outfits shortly before the show starts?
Well, its a uniform and you accept a part of your role is to be decorative. That doesn't mean you expect to be groped.
And then once they're there, they're there and its hard to walk out.
Especially if the agency wont call you again. And you've had your phone confiscated. And your bag with your money and oyster card are in the dressing room, which you can't get back to because the bouncers specially hired to keep the women in place are blocking the way. And you're drunk, because they kept telling you to drink and you were supposed to "keep them happy". You don't know what your rights are, you are questioning your own instincts because its such a prestigious event- surely you're the one with the problem? etc etc etc.
But yeah, these young women only found themselves in this position because "they have no values."