An elderly couple is having an anniversary dinner when the husband asks his wife, "Do you remember the first time we had sex together 50 years ago? We went behind this tavern, you leaned against the fence and I made love to you."

"Yes", she says, "I remember it well.

"Why don't we do it again for old times sakes", he suggests, and the wife agrees.

A bemused police officer overhears them and decides to keep an eye on the pair to make sure there is no trouble.

Behind the tavern, he observes the couple drop their drawers. The wife turns and faces the fence and the husband slides up behind her. She bends forward and grabs the fence and suddenly the two begin to have the most furious, athletic sex the cop has ever seen. It lasts for a full hour. Finally the old folks collapse panting.

Amazed the cop approaches them.

"That was something else!" he says, "How do you muster such energy at your age?"

The old man looks up, sweating, red faced and panting and replies. "50 years ago that wasn't an electric fence!"