From another angle

Goose the carpenter came to fix it this afternoon. I wasn't in, and I came home to find him on the phone to the plumber saying "I'm just going to cut out a channel in the middle of the floor"

Needless to say I suggested perhaps we locate the cause rather than treat the symptom.

So now there is a 12x12" hole in the newly built, newly plastered, newly painted wall. And we still have a hump in the floor. They - plumber, carpenter and Bossman - are coming back on Monday to have another stab at it. Which leaves us trying to convince the children not to roll themselves or any other objects up and down the hill all weekend.