Searching for Bertie

Our house is raised about six feet above street-level, so effectively there's a whole other house beneath us. You just have to duck occasionally.
It's somewhat underutilised:

Still, it's recently become home to a blue-tongue lizard, whom Mick decided to call Bertie. Why?
Why not?
His hidey-hole is directly below the bathroom:

Bertie himself has proven impossible to photograph. He doesn't mind you approaching but seems to know instinctively when a camera is being produced and disappears into one of those concrete blocks.
So far, we've worked out he quite likes bananas, but is especially fond of raw mince.

For those of you unacquainted with the blue-tongue lizard, here's a larger one I came across a few streets away a while ago.
Sadly, it didn't poke its tongue out but I assure you they are, indeed, blue: