Grandad always sent money to his grandchildren at Christmas, very generous he was too. One year, just after Christmas, he complained to his wife that none of his grandchildren ever said thank you, or sent a thank you card, or even rang him to thank him.

Roll on the next Christmas. He sent the money as ever, but this time there was an amazing transformation - in the days following, all the grandchildren came to visit and thank him and a good time was had by all.

"Well that was amazing!" exclaimed Grandma afterwards, "I wonder what caused the big change!"

"Oh, it was simple," he replied, "This year I didn't sign the cheques..."