Quote Lawrie L="Lawrie L"probably when Hull FC fans invaded the South Stand on a Saturday night game IIRC'"
I generally remember that it was only really the Hull clubs that occupied the Southstand on-mass, whatever the weather, with other clubs fans generally only coming in if it was raining or looked like rain.
I seem to remember we stopped people accessing the South Stand from the western terrace (they could still walk the long way round the North Stand though then if they really wanted) when crowds started to head up, even before they made it a separate ticket area altogether, and that is when we started having no away fans in the Southstand I think.