Boris Johnson just couldn’t help himself, could he? On the eve of the biggest set of local and national elections outside of a general election, the Prime Minister decides to go all Churchillian and send in the gunboats.

The PM has dispatched two armed Royal Navy offshore patrol vessels – HMS Severn and HMS Tamar – to Jersey to protect the island against a convoy of French fishermen threatening to blockade the island’s main port, St Helier.

They are being sent because 100 or so French fishing vessels are due to sail to the Crown Dependency tomorrow threatening to cut off food and medicine supplies to the islanders in protest against post-Brexit rules which has meant some fishermen have yet to receive licences.

The rebel fishermen have been backed by the French Maritime Minister, Annick Girardin, who has been war-like,threatening to cut off the island’s power which comes from the continent via three underwater cables. (Jersey is only 14 miles from the French coast.)

Nor does Girardin mince her words: “We are ready to use these retaliation measures. I am sorry it has come to this. We will do so if we have to.” French officials have also said they will be closing their offices in Jersey and the Channel Islands and blocking imports to France.

Jersey’s fishermen have in turn warned that blocking St Helier – the only port on the island – would be an “act of war.” As the Jersey government spokesman put it: “To threaten Jersey like this is clearly unacceptable and disproportionate. This is just the latest example of the EU issuing threats as a first resort at any sign of difficulty.”

The tit for tat over the fishing licences has been bubbling for days, prompting the minister for Europe, Clement Beaune, to warn that France would retaliate against the new fishing restrictions by being brutal to the City of London and other industries.

So what is the row about ? According to the UK’s environment and food secretary, George Eustace, it’s because 17 French fishing vessels failed to provide the data needed for Jersey to grant them a licence to fish in its waters. He added the UK – which has already granted 41 licences – is still waiting on the European Commission to provide the data needed to complete the licence applications and that they will be granted as soon as all the information is complete.

For her part, Girardin said the authorisation of 41 boats to fish inJersey waters had been accompanied by new demands “which were notarranged or discussed, and which we were not notified about”.

Jersey’s external relations minister has been trying to calm things down, holding talks with his French counterparts to find a solution.

But with political tensions high in France ahead of next year’s Presidential elections, it seems the French are taking every opportunity to bash the Brits. It goes down well with the fishermen of Brittany whose votes Emmanuel Macron is desperate to win over as Marine Le Pen, his main rival, storms ahead of him in the polls.

Which is why perhaps Boris has been a little hasty in sending in the navy patrols. For once, he has the edge on Macron and is about to win big again in the local and mayoral elections – and maybe Hartlepool too. Picking up the phone to the French president with some soothing words would have been the cleverer thing to do. Time for them both to stop behaving as school-boys. Willy-waving diplomacy can go wrong.