How to get rid of a super invasive Blackberry monster of a plant?

How to reliably get rid of a super invasive Monster Blackberry plant that took over our hedges ? No matter what I do it keeps returning.. they took over so badly I consider ripping out the hedges to deal with the BlackBerries a completely and then replant new hedges.

Anyway to get rid of those for good?

Any recommendation will be highly appreciated