Wobblers, you clearly need a ghillie suit. Suitably camouflaged, you can stake out your plot and wait for the miscreants with your trusty MkI SHUVEL.
I already has an ex-military Goretex-a-like camo outfit.
I suggest growing some ridiculously hot chillies. That'll learn 'em.
I've already got some in the greenhouse at home.
If they are going to use the 2 sackfulls of giant garlic, I suspect they'll love the scorching hot mini chillies.
There is only parsnips, carrots & leeks in crop now, and with the heavy clay soil being virtually waterlogged, I doubt we'll be having any more produce nicked.