There was one the size of a walrus (slight exaggeration there...) and I was so annoyed my camera wasn't working that I ordered a cheap one with my weekly online shop (so cheap it might be rubbish).
We can't use most deterrents, as the local cat population seem to love my garden. Lots of 'baby' slugs -- been raining here all week. How far can these things travel? I caught a bunch of then making their way down my neighbour's wall onto my decking (students -- gardens mostly untended).
