Noticed a couple of holes appeared in the grass this week, about the
size of an empty toilet roll (2inch?) the first one I run the hose
down and it never filled ( A Chaplin sketch comes to mind lol) then I
placed a brick over it. The second I just put some old bricks, cement
down it. Next day the cement had been taken out!!

What could possibly be making them and why? I presume rats though
somewhat small maybe! Why no soil spoil either? If a mole needs to
make such big hills, how come this creature doesn't?

Not too fussed as I only cut my grass to make the lawn tidy, rather
than look like a cricket pitch. Just curious.