I was talking to a chap outside one of our local allotments a little while ago and he said the allotment holders lost a lot of produce, but not to two legged pilferers, but four. A family of badgers were decimating the place. They particularly loved new potatoes and sweet corn, but seemed to be partial to everything else at various times too! Of course, when they blocked up one run, they simply came in somewhere else. We had an allotment in the early eighties and were never bothered by pilfering, but the lower end of the site backed onto woodland and the plots at that end were frequently broken into. In, out and disappear into the woods! Eventually, they put a metal fence round the whole site with razor wire on the top.