Its also tiny! It's a hand sized slab with two circles on it which can't be more than 2 inches across.

See here:
http://www.cambridge-news.co.uk/Universities/Ancient-rock-art-unearthed-in-Cambridgeshire-village.htm

Same style as cup and ring though, plus aparently grooved ware though I don't recall seeing photos of any grooved ware with circles. I thought that was mostly linear zigzags??