I have an unselectable point floating in space 2.54 km (2,540,000 mm) from the origin of my file. The largest solid in my file is approximately 200 mm long, and the longest line element about the same

It does not appear to be on a layer, (with all layers off the point is still there) and because I can't select it I also can not delete it.

The problem is that the point extends the size of my model space exponentially and is slowing everything down, it also makes finding endpoints, midpoints etc very erratic.

How do I delete it ?

In Vellum 2.7 (1997) I used to get these points when I created curves with very large radiuses, however the points were selectable, and could therefore be deleted.

I found a solid that I had imported had some problems with it.
When I selected the solid, the point would also become selected, however deleting the solid and the layer it was on, did not delete the errant point. I then compacted the model with delete history and delete empty layers followed by a save as to a new file name but the errant point is still there.

Will try exporting geometry layer by layer into a new file via .sat and see if that manages to isolate the point.