'Excuse me do I know you?' he asks. 'Yes I think you are the father of one of my kids' she says.
The man thinks back and remembers his one act of infidelity and says 'Fucking hell are you the bird I shagged on my stag do, whilst your mate whipped me and your other mate stuck a brush up my arse?'
'No' she replies 'I'm your son's English teacher!'