Now, there’s a question you have to think about before answering!
Challenge accepted. Client wanted to keep as much of the original frame as possible, so we started by cleaning up all the sharp edges left by the previous butchery then welded a stiffener into the support that had been cut. Then a 25mm square box section frame was constructed to hold it all up.
A lick of paint and the plastic seat parts refitted & we’re good to go. Commemorative plaque installed at the owner’s request.