Brain Teasers (page 106)

Four old retired guys are walking down a street in London. They turn a corner and see a sign that says, "Old Timers Bar - All drinks 10p." They look at each other and then go in, thinking, this is too good to be true.
The old bartender says in a voice that carries across the room, "Come on in and let me pour one for you! What'll it be, gentlemen?" There's a fully stocked bar, so each of the men orders a martini. In no time the bartender serves up four iced martinis—shaken, not stirred—and says, "That'll be 10p each, please."
The four guys stare at the bartender for a moment, then at each other. They can't believe their good luck. They pay the 40p, finish their martinis, and order another round. Again, four excellent martinis are produced, with the bartender again saying, "That's 40p, please." They pay the 40p, but their curiosity gets the better of them. They've each had two martinis and haven't even spent a £1 yet.
Finally one of them says, "How can you afford to serve martinis as good as these for a 10p a piece?"
"I'm a retired tailor," the bartender says, "and I always wanted to own a bar. Last year I hit the Lottery Jackpot for £25 million and decided to open this place. Every drink costs 10p. wine, liquor, beer -- it's all the same."
"Wow! That's some story!" one of the men says.
As the four of them sip at their martinis, they can't help noticing seven other people at the end of the bar who don't have any drinks in front of them and haven't ordered anything the whole time they've been there.
Nodding at the seven at the end of the bar, one of the men asks the bartender, "What's with them?"
The bartender says, "They're from Scotland. They're waiting for Happy Hour when drinks are half-price."