Sorry no one has answered. I see in the USA there is a lot of information on this highly invasive plant on line, if you have a look there are ways to destroy the roots. The University of Pennsylvania has a lot of information on this.

Thanks Drc726. I was thinking about using a flame thrower but decided the neighbors might object. :) I can see this is going to be a long term project.

I think you might be right, but it has to be done I fear!