It did happen about Twenty years back, but it was a Ching-Chong dispute.
The reason that I know is because one of the main instigators of the Machete fight in Dooblin was a regular Bookie customer of mine, he was a good customer easily dropping a 'Bag a Sand' a week.
He did have a dispute with my assistant manager once on my day off, over a bet that was laid 'Late' while in Running, my young assistant manager refused to pay out and the Ching then put Two small pencils between his fingers, fortunetley he did take the Pencils out of his fingers before his attack, but he still stuck both of his fingers in to my assistant mangers eyes.