Brexit has been blocked by the most head-banging of Brexiteers. Leavers are now hoping for a sweet paradox of their own. They are looking to President Emmanuel Macron, a remainer super-hero, to boot Britain out of the European Union next week.

Recent remarks made by the French president suggested that he might summon the spirit of Charles de Gaulle (vintage 1963 and 1967) and veto – come what May – extended British membership of the EU at the Brussels summit on 10 April.

Will he? Before a meeting with Irish taoiseach Leo Varadkar, on the steps of the Élysée Palace on Tuesday, Macron blew hot and cold. “Should the United Kingdom be unable … to propose a solution backed by a majority, they will de facto have chosen themselves to leave without a deal,” he said. “We cannot avoid failure for them.”

Le Brexit dur, then? No, not really. Macron went on to say that “credible justifications” for an article 50 extension did exist. They might include an election, another referendum or softer proposals for Britain’s future relationship with the EU. He and other EU leaders would be “open” to clear ideas if Theresa May would only put them forward at the emergency summit in Brussels next Wednesday.

Has Macron changed his mind? More likely he has changed his public tone, under pressure from Berlin and Dublin. It was never likely that the French president would defy the other 26 capitals and block an article 50 extension on his own. He remains, nonetheless, the leader of the impatient camp within the EU27.

May’s new plan – to seek a short delay until 22 May to push through a hybrid Labour-Tory Brexit – both simplifies and complicates life for Macron and the others. If she has a deal by 10 April, the short extension to 22 May will be signed off easily. If there is no internal UK deal, there will be huge reluctance to declare a no-deal Brexit, but also huge reluctance to extend the Brexit psychodrama.

In resolving this conundrum, Macron will play a pivotal role. He, like many other leaders, is opposed to giving May a blank cheque to find a solution in the next seven weeks. That may lead to Britain crashing out of the EU on the day before the European elections.

Other leaders could offer a longer delay, in return for a British commitment to organise European elections, and refrain from messing up EU decisions on a new commission president and a new five-year budget plan. Macron is viscerally doubtful about any such rollover – even though he has reasons of his own to fear a hard Brexit.

The delays to Eurostar caused by striking French customs officers are only a taste of what an unregulated Brexit might bring overnight on the eastern side of the Channel. Macron’s hopes of outlasting the fading gilets jaunes rebellion depend on a modestly recovering French economy. A hard Brexit would be economically calamitous for Britain, disastrous for Ireland and painful for France.

Northern French fishermen rely on “British waters” for 60% of their catch. The last thing that Macron would like to see just now is to see fishermen in yellow vests blocking Calais harbour or the entrance to the Channel Tunnel.

All the same, Macron is the most hostile of all EU leaders to another year of wrangling with Britain which would divert energy and attention from his own plans for a European “renaissance”. Even the most Europhile and Anglophile commentators in France are starting to say that a “clean if painful” break with Britain might be better than another nine to 12 months of poisonous uncertainty.

François Heisbourg, the British-born, Franco-Luxembourgish, former head of the International Institute for Strategic Studies in London, carried on a long Twitter conversation with anxious French followers this week. One of them concluded that keeping Britain in the EU would be a “metastasising cancer … better to cut off the sick branch to preserve the trunk”.

Heisbourg commented: “Note to UK readers: this tweet is fairly typical of remain-friendly French Europhiles. You can imagine what the mood is in other quarters.” Those “other quarters” include the Élysée Palace. Macron has bet his presidency on facing down “leprous” populism at home and fighting the rise of nationalism in the rest of the EU. A Britain “forced to remain against its will by elitist Europeans” might be a gift to Marine Le Pen and other populists in the European elections in May.

If the consensus goes in favour of a long extension to article 50, the French president will doubtless grit his teeth and claim the credit. Brexiteers would be foolish to count on the French president as a one-man Maginot line. He will, all the same, be the leader of a summit faction that resists lengthy extension of article 50 without clear proposals and guarantees from May. A second referendum? A general election?

It is Macron’s view that it’s up to Theresa May to propose such solutions, not the EU27. He may yet, de facto, end up becoming an unlikely hero for hard Brexiteers.

• John Lichfield is a journalist based in France