In the European Men Championship 2005, one bowler made a very bad mistake. I really don't recall his name or nationality, but couple of minutes after he rolled his 12th strike, while he was "enjoying" his triumph, he deliberately step on the foul line!
As Robadat stated above, according to the rule, either he had to step down from the approach, or some other bowler must have rolled a ball next to him to call his shot is ended. But, as you may understand, no body rolled any ball after his and he had not step down from the approach till that moment!
So, although couple of minutes had passed from his shot, it was called violation of the foul rule and he received 0 count for the last shot!
"Intentionally" 290 with 12 strikes! Nice

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Regards,
Natal