I suggest you look up the judgment from the Navair Bankstown mid air.
The ATCs where given 30% of the blame because the judge said ATC could see the two aircraft and therefore had a duty of care.
For a decade after, ATC separated VFR from VFR to IFR standards in Sydney.
I would have to orbit at Hornsby for ten minutes while they separated my helicopter from the channel ten chopper with IFR standards!