A strong disinfectant - my cat runs a mile when I'm cleaning the kitchen with it, and he justs sits in the laundry room looking threateningly at it... then he backs off further when I start cleaning the floor in there too

so mean!
But how you'd apply it in the garden I don't know. I have a couple of final ideas - some cats are afraid of their reflection (although not mine, he just cutely tries to look around the mirror you hold up at him). On the off chance these are you could:
1) Put some old CDs face up in the soil in your garden - a friend who lives on a farm does this with AOL CDs to scare the birds
2) Cut the top off a soda bottle, leaving the cap screwed on, and fill it with water, burying the whole contraption in the soil and remembering to refill the water every few days. Meant to have the same effect, plus the cat gets wet if it tries to go for its relfection, which it won't like. I know we used to do this long ago and it worked relatively well.
They also do gadgets that are meant to emit sounds that cats don't like, but I for one know of no such noise neither do I believe such gadgets (expensive as they are) work that well. Any anti-climb paint is useless. My cat regularly jumps 7 foot from floor to wardrobe top in the house, and if pressed a cat can jump a little higher still and scrabble the rest, but I really doubt your fences are 8-10 feet high are they?
A slightly more stripy
Gee_4ce, and more than just Something British...
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