I ran very fast the day a friend pulled a live mortar round out of the ground. We were walking across a field when he kicked a metal tube sticking out of the ground (the field and the footpath which ran across it had recently been ploughed) and pulling it out we found the fins attached which let us know what we'd found. Bomb disposal came and did a sweep which turned up a couple more of them and some mills bombs and blew them up leaving quite a crater. There's still tons of stuff in the fields around us as the whole area was used as training grounds for Canadian troops during WWII and they left a lot of stuff behind, although they didn't leave the hamlet of Balsdean behind as they used that as target practise.