Four Royal Navy patrol ships will be ready from 1 January to help the UK protect its fishing waters in the event of a no-deal Brexit, in a deployment evoking memories of the “cod wars” in the 1970s.

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.