Tree Hole - NOT amateur radio

This was in a tree at Anglesey Abbey seen last week.

One wonders what lives within! I expect the kids love it and imagine all sorts!

What made this? - NOT amateur radio

A few days ago we went to Anglesey Abbey which is about 4 miles away. We saw this hole, but I am not sure what creature made it. Moles usually leave a pile of earth. This hole had none. My guess is a mouse or a shrew? The hole was about 3cms (just over an inch) across.