'Mind the gap'
or
avoid the void.

Those gaping chasms that
look at you and you?

well, you wonder,
what happened to that dear old lady
who lived in a shoe and what became of
her children?

and you do that because you know that
the world's flat, there are no voids or gaps,
there are only the sharp edges of reality.

The tannoy's a ploy,
it's the voices in your head
you've got to watch out for.