Fox Repellant

They do it here too - never caught them at it but because the digging eventually stops I always assume it's the cubs trying to find the 'treasure' they think is there having been drawn to it by the smell of chicken pellets (blood, fish and bone even worse - had to stop using that completely.)

It is said that male human urine deters them - don't know how effective it is but not exactly a practical proposition unless you're prepared to smuggle bottles of pee to the allotment! 

I chuck pieces of chicken wire over young crops, especially if I've used chicken pellets in the area - seems to be enough to deter them and they don't seem to bother when crops have grown a bit bigger (possibly because the smell has gone, or maybe they just learn that chicken poo doesn't actually taste that great!)

Male urine deters them. Fill a jar and drizzle it round the edge of the plot.
We used to do this years ago, when we put our dustbins (yes the old type, not wheelie bins) out in the rear of our houses. The foxes used to raid them regularly. But doing that trick stopped them doing it. They just moved on to streets or bins that did not do it.
Have done it in the garden for years, just sprinkle about four times a year, and it keeps them away. My next door neighbour does not and they have fox holes and their mess on their paths at least once a fortnight, sometimes more. I have not told them what I do.

One year at our rather large site in Oxford we kept finding single shoes, along with ripped open bags of fast food waste, at many locations around the site. We eventually worked out that it was foxes who had brought them in.
Last year, in one of my giant raised beds, there was a deep, long curving hole dug through my line of parsnip seedlings. At the bottom of it I found a very stylish red shiny leather women's high heeled shoe....