Jack and the Whisky challenge

When Jack was young man he was attending a big do put on by a councillor with plenty of food, drink and entertainment. All the locals had gathered and he was standing with his mates wondering what to do.
"The beer's a bit warm, mate," Jack said to his friend.
"There's a whisky bottle sitting lonely on the bench over there," his friend replied.
They both looked at the bottle longingly and Jack came up with a plan.
'Tell you what, Mate," said Jack, "What about you get near the bench and I go out there and turn off the generator which will turn off the lights. You grab the bottle. I'll turn the lights back on and Bob's your uncle."
A moment later Jack slipped out of the tent, turned off the generator for a moment, turned it back on and snuck back into the tent looking as innocent as a lamb.
"Well?" he asked his mate as they huddled in the corner.
"Nope," said his mate.
"What?" asked Jack.
"Some other bugger had the same idea and pinched it before I got it!"