Nasty surprise
 

A bloke is walking home through the park one night when a woman pops out of the bushes and says,
"You can fck me as hard as you like for a tenner."
The bloke agrees and they go off into the bushes together. He's just ready to cum when a policeman shines a torch on them and says,
"What the hell do you two think you're doing?
- "I'm having sex with my wife," replies the bloke.
"I'm sorry sir, I didn't know it was your wife."
- "Neither did I until you shone that bloody torch on the bitch."