A guy comes home one day and finds his wife packing a suitcase "What are you doing?"
"I'm moving to London" she says "I've heard that the prostitutes there get paid 400 quid a time for what I do for you for free!"
So the guy grabs a suitcase and starts packing.
"What are you doing?" she asks.
"I'm coming to London as I want to how you survive on 800 quid a year!"