There is a one off golden opportunity to prove or disprove the link
and that is by making the whole of the ismuth from say Plymouth to Bristol a fully culled deer & badger free zone that is also cattle free ( gosh that would be expensive ) for ten years or so to enable pathogens in the soil to die out and then reintroduce disease free cattle for five or more years testing all the time every four months or so whilst keeping up with the culling of any badgers or deer seen .
Though to me common sense would indicate that this would only mirror the Irish cull results .
It would also be wonderful if Mr & Mrs brock and their kiddiewinks would all come to the nice person with a syringe to get anti TB vaccinated , get tagged & tattooed then gaily pop along to tell their neighbours to come and get sorted as it is free and enhances their life quality .
I think the ineffectiveness of any vaccine has to be a massive reason for also allowing a cull to start and be carried on for a reasonable time to see if the findings are correct .
What did it cost in compensation alone to the UK farmers last year £ 4.3 billion
That's not to mention the large numbers of farming folk who have had massive secondary uncompensatable losses going out of business.
I suppose the thoughts behind the culling is a bit like cutting or spraying weeds .
Keep cutting/spraying the weeds down and the problem become a lot more manageable . Don't do anything and you'll get overrun with them and lose out big time .