In the meantime, does anyone have any good ideas for how to stop the cats bringing frogs in? I would have thought frogs didn't taste nice enough for a cat to want to bring them up to my office in their mouth, but I've just evicted the second one of the day... actually Orac (it has been her both times) spots that I am Not Best Pleased and then takes the poor thing back downstairs. I pick it up in a teatowel from wherever she happens to be watching over it, and put it out in the front garden.
Still, this is getting a bit old. Suggestions appreciated ("putting a muzzle on the cat" may not quite work)
(ETA: Frog 3 was just brought into my office while I was on the phone to a (thankfully quite understanding) client. Thanks, Orac.)