Steve sees an old school friend of his, Mark, sitting in the corner of the pub, looking thoroughly depressed.
'Hello mate, What's up?'
"It's my wife - she's going to leave me"
Mark then explains that his wife was fed up with him coming home smashed and said that she'd be off the next time he did it. Steve could see that he was absolutely rat-arsed, and had thrown up over his jacket.
"Look Mark, have a few cups of black coffee and take a stroll round the block. That'll clear your head a treat. Put this £20 in your pocket and when you get home tell Sue that some bloke threw up over your jacket and gave you the £20 to have it dry-cleaned".
Mark follows these instructions to the letter and when he gets home, senses that Sue is falling for it.
"Oh, poor you!" She says, "that must have been horrible for you - but where did that other £20 come from?" She asks, pointing to a second note.
'Oh, that?', he says 'that's from the guy who shat in my pants...'