A married couple is driving along a highway doing a steady forty miles per hour. The wife is behind the wheel. Her husband suddenly looks across at her and speaks in a clear voice. "Darling," he says. "I know we've been married for twenty years, but I want a divorce."
The wife says nothing, keeps looking at the road ahead but slowly increases her speed to 45 mph.
The husband speaks again. "I don't want you to try and talk me out of it," he says, because I've been having an affair with your best friend, and she's a far better lover than you are."
Again the wife stays quiet, but grips the steering wheel more tightly and slowly increases the speed to 55.
He pushes his luck. "I want the house," he says insistently.
Up to 60.
"I want the car, too," he continues.
65 mph.
"And," he says, "I'll have the bank accounts, all the credit cards and the boat." The car slowly starts veering towards a massive concrete wall. This makes him a wee bit nervous, so he asks her: "Isn't there anything you want?"
The wife at last replies - in a quiet and controlled voice. "No, I've got everything I need." she says.
"Oh, really?" he enquires, "so what have you got?" Just before they slam into the wall at 75 mph, the wife turns to him and smiles.
"The airbag."