When is a cannon ball not a cannon ball?

You may remember a post below that mentions a cannon ball found on Eggardon Hill by Paul. Well, a good friend of mine, who is into geology and fossils, tells me that chalk strata can be riddled with spherical voids into which iron rich water can gather. This hardens into a solid mass and can create spherical iron shapes which are then eroded from lower down into the top soil. The only way to find out is to cut the artefact in two. So if you want to do that Paul...