An updqate. I read the manual 6.4 on Migrations. I've added a migrate='tablename' aramter to the table definition call. It seems to work.
So I guess I've disconnected the table definition from the Web2py table history. So far so good. So I have a more general point. "Is it 'better' to manage database designs using the Web2py model or better to manage the database using the DB utilities and keep the model in sync?" I understand the web2py model route ought to be better, but this is the second time I've lots hours messing around with out of sync database and models.