This week we're turning our attention under the sea. French and British fishing boats recently faced off in the English Channel over who had the right to fish for scallops. That situation seems resolved for now. But it's raised the spectre of post-Brexit fishing wars between the UK and a host of European nations who currently fish in British waters. Between them, they net catch worth over £350 million annually. Can the UK really close its waters to foreign fleets – legally, and practically?