If that did happen you'd have a good case from the Human Rights Act because it becomes indefinite imprisonment. The UK is still following the ECHR as well. But

If that did happen you'd have a good case from the Human Rights Act because it becomes indefinite imprisonment. The UK is still following the ECHR as well. But arguing these theoretical untested-because-they-never-happen edge cases isn't exactly pushing forward a good case for this law having been "badly written." There's seemingly no problem with it in practice.