The usually uncontested waters of the English channel were last night roiled by clashes between French and English fishing boats in a rapidly escalating row over scallops – and Brexit is the underlying cause.

In scenes that will have the tabloids dusting off old tropes about the battle of Agincourt – where Henry V bravely fought off our continental neighbours against all odds – six English boats held their nerve as they were rammed, insulted and pelted with rocks by 35 French boats.

At the heart of the dispute is the allegation that English fishermen have been abusing a legal loophole to take more than their fair share of Normandy scallops, which the French say are iconic to their cuisine, stripping…