Once I borrowed a metal detector to find a metal charm I was pretty sure was lost in a 10' square area of lawn. For kicks, I checked out the rest of the yard, and all I found was an old metal beer can that was probably from when the house was built. (It was the kind with the soldered seam on the side, and the top and bottom disks soldered to the body, and had one of those pull tabs that doesn't stay with the can.) What a thrill. To be fair, though, that was in the midwest US, so some yard in jolly ol' England might have some old bullets or treasure hidden from the Count's guards or unexploded ordnance.