Tristan I wonder how dense is the pan you mention, because bulls are heavy animals for sure. Possibly it justifies a forking, not that I want to encourage that, only in exceptional circumstances.
If slugs are as bad as you say, you could try skimming off the turf and then composting over, to avoid using cardboard, and in order to have first-year crops of slug-sensitive vegetables.
Maybe try half the area like that and the other half with cardboard, also you could grow leeks etc in that part.
