Sevco fan on the way home from the pub encounters a prostitute in a dark alley. "How much furra shag" says he; "£20" says she and they get down to business. Next thing a cop walks into the alley and shines a torch on them.
"Hey! what are you two up to?" says the cop
"Sorry officer I was just having sex with my wife"
"Sorry sir I didn't realise it was your wife"
"Neither did I til you shone that fuckin torch on her face".