Watch Guarantee

This Derry man who's a fanatic about watches, but has never been able to afford one, wins a million in an accumulator at the bookies. So the first thing he does is get on a flight to London, go into the biggest jewellers he can find in Bond Street, and ask for the best watch in the shop.
'I think this is what sir is looking for,'says the smarmy assistant. 'It's solid gold and platinum, encrusted with diamonds; it took three years to make by the best craftsmen in Geneva, who destroyed the plans when they'd finished it; and inside it there is the finest in state-of-the-art timekeeping technology. You will never need to alter it from the moment you put it on, for it's guaranteed not to gain or lose a second for the next thousand years.
'I'll take it,' says the Derry man, writing out a cheque for £250,000.
So he gets the Shuttle back to Northern Ireland and that night he's sitting at home watching the TV when News at Ten comes on. He looks at the watch and it's showing a quarter past six. Enraged, he jumps up and runs into the kitchen, where he finds his youngest son feeding the five greyhounds.
'You wee bugger,' he says, smacking him round the back of the head. 'Have you been messing around with that TV?'