[support] Switching anonymous access to the whole site on and off

Hi,

What would be the quickest way to switch anonymous access to a site on and off? We have a large and fairly complex site almost ready to go, but we need third parties (with logins) to fill in and test content before it goes live.

As we've a lot of modules we've got quite complex permissions already, so checking and unchecking a lot of fields would be difficult to do quickly. Is there any "master switch" permission we can fix to lock it all down?

Otherwise, would it be worth putting a check for $user->uid in our template.php, and bouncing anyone to user/login if they don't have it set? Anyone see any problems with that?

Many thanks, J-P