Neither Doug, break marks suggest it initially cracked at half thickness across full width on the underside and had been like that for a little while. The enthusiasticly driven minor roads on the day of final parting finished off the other side. I did lightly chamfer edges of wing mount hole on replacement in case there was a stress riser there but guess it's inevitable presence of this hole makes for weakest point.
Note there is a deliberate slight bend in bracket to match the jaunty angle the shock absorber sits but this is comfortably outboard of hole/crack.
