A bloke is driving around in his Porsche in the English countryside. He stops outside a field full of sheep, walks up to the shepherd and says, "I've got an offer. I'll guess how many sheep you've got in this field, and if I guess right, I get to take a sheep with me. If I guess wrong, you get my car."

The shepherd thinks he's on to a sure thing and agrees.

"137" says the driver.

"Damn me, you're right," says the shepherd and dutifully hands over a sheep.

The man walks away, stuffs the sheep in his car and is about to drive away when the shepherd knocks on his window. "I've got a proposal for you." says the shepherd. "If I can guess what you do for a living, I get to take your car. If I'm wrong, you can have all my sheep."

"Done," says the driver

"You're a consultant," says the shepherd.

"Bloody hell! How did you guess?"

"Easy. You come in here uninvited, you tell me what I already know, and then you charge me for it."