You need a Dangerous animals licence to keep wild boar. Whilst this is not too onerous and mostly common sense stuff - they check the security of your fencing and so on, it is not to be taken lightly. We were looking at keeping boar but the insurance cost was too high, as our land has a public footpath and adjoins houses. A friend of mine has a wild boar boar that he crosses onto commercial pigs and fully grown it is a terrifying creature. It has knocked down and eaten two of the 8 foot dense concrete block walls in its pen and is a quarter of a ton of pure malevolence. I now prefer to shoot the things in the wild out in Slovakia and bring them back dead rather than breeding them.