Inside the polytunnel as of today, no cover crop as the water to the allotment is turned off for the winter. So the next best thing is a mulch of compost covered with an opaque but permeable membrane which prevents weeds from growing but allows gas exchange. Underneath the soil is damp and there are plenty of worms. I doubt it'll freeze over even if it gets really cold outside. I am concerned that it'll be a cosy place for rats and mice to spend the winter - we'll see in a few weeks time when I get some samples for the first soil test of the year.