The 80-metre-long armed vessels would have the power to halt, inspect and impound all EU fishing boats operating within the UK’s exclusive economic zone (EEZ), which can extend 200 miles from shore.
Operating word being ‘can’. The actual EEZ around most of the UK is laughably far from being 200miles. See pic. The EEZ around the overseas territories are a different matter, and part of the reason for having them.
https://www.theguardian.com/uk-news/2020/dec/11/four-navy-ships-to-help-protect-uk-waters-in-case-of-no-deal-brexit