Fridays Joke: father of one of my children?

A bloke is in a queue at the Supermarket when he notices that the rather dishy blonde behind him has just raised her hand and smiled a hello to him. He is rather taken aback that such a looker would be waving to him and although familiar he can't place where he might know her from, so he says, "sorry but do you know me?" She replies "I may be mistaken, but I thought you might be the father of one of my children !" His mind shoots back to the one and only time he has ever been unfaithful, "Christ!" he says "are you that stripogram on my stag night that I sh*gged on the snooker table in front of all my mates whilst your mate whipped me with some wet celery and stuck a cucumber up my a*se!?" "No" she replies coldly,"I'm your sons' English Teacher"..