Pigs can sure dig up roots and about another foot down if they feel like it, I know we have wild boar on our land. It does depend on what you want to do with the land afterwards. Often the best way to clear something if you don't need to use it for a couple of years is to cover it with something like an old carpet " preferably hessian backed carpet, otherwise you end up with lots of loose stringy fibres from past experience. You will probably have to weight it down to stop the blackberries growing back through it, I know they are quite determined. Although Kate may have better ideas

Don't worry, you'll get there, just stick with us and have a giggle along the way