> I believe the strategies that helped tip the balance was salami-slicing to just abolish trade rather then total abolition while arguing that continued trade would lead to slave rebellions as had been seen in French colonies thus it needed to be stopped not just out of moral necessity but national interest too.

Y'see, I count that as "the bare minimum done because they were forced to not because they wanted to".

Knowing that if you don't, it's going to be expensive is part of "being forced to". Getting around to it only when there's overwhelming pressure in one direction rather than 50%+1 is "dragging your feet".

The margin of what passed is on the one hand, the fact that it was only peaceameal — as demonstrated by literally all the other years on that list — is the other side of that coin.