This bloke walks into a bar and over the next couple of hours proceeds to get increasingly drunk.
Suddenly he spots a guy in the corner with a group of friends and begins to verbally abuse him.
"Oi you!" he shouts ."I've shagged your mum!!"
The man carries on drinking trying to ignore the guy's drunken rantings.
Half an hour later the drunk stands up and renews his abuse.
"Oi you !" he shouts even louder this time "I shagged your mum up the bum!"
The guy in the corner turns his back on him and continues talking with his friends although by now visibly irate.
Half a hour later the drunk pipes up once again. "Oi you, your mum sucked my dick!!"
By now the guy in the corner has lost his cool, he stands up furiously and retorts,
"For fucks sake Dad go home, you're embarassing me !"