Building new run - what size mesh?

We got the 1/2" x 1", and it's perfect.  Think  it was 1 mm diameter.  If you can bury it deeper than that, at least 12", better still 18".  We were hampered by tree roots so hammered in wooden posts in a row where we had problems, and used very deep kickboards where we could, and sunk them fairly deep as well.

Another trick is to fold the mesh out, so that if a fox did dry to dig down, they'd just get the claws caught up.  We actually burried strips of off cut mesh in the outer side of the trench around the mesh boundary.  The cut ends are sharp, and would put anything off digging there.

The visible 'pen' is like the tip of an iceberg, all the real work and sweat went into the trenches.  But I think that's the best way.

1mm/19g all around should keep out the most determined of foxes, but remember the strength is also in the fixings to the framework.

Rob