It's behind you!

And it is an 'erratic' which you will have surely spotted already. The rock is clearly silurian and the material underneath is limestone. It was only deposited a few hundred thousand years ago so it could roll off downhill at any time.
The gov finished her coffee and moved out of the way before anything untoward happened.
Later we spent a long time looking at brachiopods, crinoids and corals in the rocks and even longer turning over frost shattered limestone looking for bits to take home, with some success I may add.
Tomorrow is a big blip-day, watch this space.........