It does seem to be a quality of the mineralogy of the area. There are a lot of calcite ( I think ) inclusions in the rocks in the neighbouring field. It was the way the marks differ on the pillar which threw me. It was quite some time afterwards that I thought of the possibility of it being a multi stage thing.

If it's not petrified wood I really hope a good geologist can explain exactly how the marks were formed or it will bug me forever.