Quick -- What does "off pat" mean to an Australian?

[Jeff Barr]

FoRKers, please help.

I'm working on a business plan and one of the comments
about a fact was that "we need to have this off pat".
This from an Australian lawyer.

Does this mean that I need to hide it, say more about
it, or just know what's behind it?

Google returns a lot of interesting things, but nothing
that's helpful here.

Thanks,

Jeff;

PS - Why do we have all of these incompatible versions of
     English, anyway?