She's my wife

Late at night this guy runs into a pub and demands a glass of water from the landlord.

The guy drinks it in one gulp¹ then asks for a second glass.

Six pints² later, and he has recovered enough to speak. "Thanks," he croaks³.

"That's one hell of a thirst you've got," says the landlord.

The guy says: "Any man would be as bad if they'd just had sex with the woman in my car.

She's insatiable. She wants me to go right back out there and do it all again, but I can't."

"Where's your car?" the landlord asks.

"At the roadside," the guy gasps⁴.

"Tell you what," says the landlord, "you watch the bar for me while I nip out and take your place."

"Be my guest," the guy says.

So the landlord goes outside and gets in the car. It's totally dark, so the woman doesn't realize she's with a different man. And they get right down to it, humping away.

Five minutes later there's a knock on the window. It's a cop, and he shines his flashlight on the naked couple.

"What's going on here?" he asks.

"It's all right, officer," explains the landlord, "She's my wife."

The officer replies apologetically, "Oh, sorry sir, I didn't realize."

Look at the woman the landlord says, "Neither did I till you switched on that damned light."