A grandmother was left petrified when she was sent a police machine gun in the post by mistake. The package was delivered by a courier to Catherine Roots when it should have been sent to firearms officers at the nearby police HQ. Mrs Roots had been expecting a horse harness in the post so opened the package thinking it was that. Instead, she found the Heckler & Koch black sub-machine gun staring back at her. She called the police and two armed officers turned up and took it away. Red-faced officers later explained a gun supply company made a one-digit...