Sutton harbour, Plymouth, 8am. The flutter of the trawlers’ flags provides a rhythmic accompaniment to the clamour of the dawn fish market. Up and down the jetty, captains bark at the deckhands to unload their catch faster: freshness and speed are key to turning a profit. On the pier awaiting the haul are the fish merchants, ready to deliver the catch to restaurants across the country, so they can be served up within 24 hours of being landed.

One of the boats tethered to the jetty is a scallop dredger, which has been dragging the fisherman’s equivalent of a plough along the seabed for the past two days, collecting highly-prized king scallops. The skipper has phoned the merchants from his boat in advance to negotiate