Liz, you might have a point - we are prone to being invaded by another very sneaky (and hungry) cat, who cleans out the food bowls and manages to avoid being caught. However I'm doing my best to monitor that the cat has had sole access to (and has eaten) the dosed food and so far we've been able to witness the crucial top layer or so being devoured.
At one time the cat's food was also being stolen by some small rodents who were living behind the washing machine - talk about taking the p***! She's a tad deaf, you see, our Cleo, and the first she knows about it is when she discovers the empty bowl. She does know some good swear words, though.

Anne