dividing wall

The year before we bought our house my next door neighbour hit the dividing wall at the back of our house causing it to become unstable. The previous owners of my house paid for the wall to be built and it is on the boundary line. Who should pay for the wall to be rebuilt or should we pay half each?

Oddly enough, this raises a whole slew of legal possibilities and possible arguments on both sides. Just a few:

1. You bought as seen - you don't have an entitlement.
2. The house was devalued by the cost of repairs when you bought. Your vendor is at a loss for the initial trespass and could sue for it
3. Less likely, but I suppose possible: the right of action against the neighbours was 'sold' to you and you could now sue them for cost of repair of wall.
4. Instead of trespass, you might have an action in negligence against the neighbour.

and so on.