Hmmm. I couldn't find The Polisher or the Fyfield Cup Marked Stone on there, and they have pretty good provenance.
So from one point of view, the fact that the Kenward stone has been deemed worthy of inclusion on Pastscape means there must be at least some doubt if it's natural or not.

I did notice that Long Tom is described as 'finely dressed sarsen'. Given that they have to go through all that clart with burnng pits just to split the things, I'm genuinely curious as to how stonemasons 'finely dress' sarcens. Cue quips about stones wearing brocaded fur-trimmed coats etc.. ;)

Thanks for the link baza although they are quoting the same sources that I consulted, ie the excavations in the 1920s. I just think that it should be re-assessed in the light of our present knowledge. I'm not an expert in this area of possible carvings so the more opinions (of those who have seen it) the better.
My own feelings?.......Some marks are surely natural but what process (erosion or lost fossils[?]) could have caused the peculiar parallel wavy lines?