"It was quite funny to be honest — me and my nan were just holding them in the garden," George Cheetham said of the devicesJohn and Pam Heritage with their grandson; World War I anti-aircraft shellsCredit: Kennedy News and MediaNEED TO KNOWGeorge Cheetham was cleaning out his grandmother's garage when he found World War I explosive shells that "still had tops on"The pair reported the discovery to the police, and a bomb squad was called in to saf…