The thing about badger culls is that if you kill a local population, other badgers roam in and find an unoccupied habitat, together with unoccupied setts. So they move in. And if the previous occupants had TB, the newcomers will pick it up.
Therefore the only way to deal with TB transmission by culling badgers is by exterminating the UK badger population totally.
Which would not be politically acceptable.
Therefore farmers must use other means to make our herds safe from TB, which is an increasing threat to us humans.
I am not expert, but it involves vaccinating herds, possibly vaccinating badgers (yes, it is on the cards) and most importantly, increasing the general resilience of herds by letting them live lives as near normal as possible.
I'm not an expert, but I can manage logic.