Being a geek, I worked out, as a ball park figure, that the roundabout is roughly 6m in circumfrence, even at 10k an hour road speed, the roundabout would have been doing about 25rpm.
At point of "take off" (for the two chavettes (priceless)) the roundabout was probably doing 3 or 4 times that!
Was the roundabout designed for that? In this case two girls got flung off, what if the whole roundabout had come off?
I would suggest a sign depicting the scene with a big cross through it be established at all parks, but then I though a sign with the word "idiot" and a cross through it would be a better catch all sign.