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.. ;)