A Shocking Affair

The husband leaned over, and asked his wife, "Do you remember the first time we had sex together, over fifty years ago? We went behind this very tavern, and you leaned against the back fence, and I made love to you?"
"Yes, she said. "I remember it well."
"OK," he said. "How about taking a stroll around there , and we can do it again, for old time's sake?"
"Oh Charlie, you old devil. That sounds like a crazy idea! But ok!"
There was a police officer sitting in the next booth, listening to all this, and having a chuckle to himself. He thought to himself, "I've got to see these two old-timers having sex against a fence. I'll just keep an eye on them so there's no trouble."
So he followed them, as they walked along, leaning on each other for support, and aided by walking sticks. Finally they got to the back of the tavern and made their way to the fence.
The old lady lifted her skirt, and the old man dropped his trousers. As she leaned against the fence, the old man moved in.
Suddenly they erupted into the most furious sex, that the police officer had ever seen. This went on for about ten minutes. Both were making loud noises, and moaning and screaming. Finally, they both collapsed on the ground. The police officer was amazed.
After about half an hour of lying on the ground , the old couple struggled to their feet and put their clothes back on. The Policeman thought, "I've got to ask them what their secret is".
As the couple passed, he said to them, "Excuse me, but that was something else. You must've had a fantastic sex life together. Is there some sort of secret to this?"
The old man replied, "Nope! Fifty years ago, that wasn't an electric fence!"