France suddenly faces the real possibility of a presidential run-off between the Eurosceptic hard-Left and the Eurosceptic hard-Right.

The meteoric rise of Jean-Luc Mélenchon on a Proudhonist - if not Bolshevik - platform has changed the equation. He is just as nationalist and radical as the Front National's Marine Le Pen, and certainly more dangerous for the owners of capital.

"Absolute catastrophe. Mélenchon is the Venezuela scenario, Le Pen is the Argentine scenario," warns Pierre Gattaz, head of the French employers' federation MEDEF.

Both candidates are anti-German, anti-American, anti-globalist, anti-NATO, and pro-Putin. Both want to rip up the EU Treaties. Both want some sort of parallel currency or sovereign monetary control.

Both are viscerally hostile to financial markets and to liberal labour reform. Both want a bigger French state financed by borrowing, and damn the deficit. The ideologies merge. 'Les extrêmes se touchent', as the French say.

If the complex arithmetic of the first-round election on April 23 leads to a duel between these two wings of the French Resistance, the outcome will be shattering for monetary union and the European project.

While it is true that neither would have a working majority in the French parliament, this alleged safeguard raises as many questions as it answers. Does anybody think that the euro experiment - already fragile and damaged - can survive for long if one of its two anchor states is embroiled in political civil war with no functioning government?

And:

It is fitting that Mr Mélenchon's "Left Front" movement has been renamed "France Insoumise" (Unsubjugated France). He is playing the Left-nationalist card as hard as Mrs Le Pen plays the Right-nationalist card. 

Among his policies are a 32-hour week, retirement at 60, a top tax rate of 90pc, effective confiscation of any income above €400,000, a higher wealth tax, a luxury tax, recruitment of 60,000 more health workers for a larger state heading for 60pc of GDP, and fiscal slippage of €175bn over five years according to the Coe-Rexecode institute. Mr Macron rightly calls him a "revolutionary Communist".

Whether voters really would vote for Mr Mélenchon's fiery cocktail in preference to Le Pen's more cautious bourgeois variant is far from clear, once they discover what he is actually proposing. Either way, a victory by one or the other would be an earthquake.

The political contours of Europe have changed in this election. It has shown that the Brussels and the EU system can no longer rely on the emotional consent of the French Left.

David Fuller's view

This is all very exciting, or terrifying depending on your perspective. While interested, I am only a distant observer and although looks can be deceiving, in the photo posted in AEP’s column, Jean-Luc Mélenchon looks like a kindly gentleman and he has been described as articulate by the press. That does not remind me of a “revolutionary Communist”, as he has been described by Emmanuel Macron who currently has a slight lead in the French polls.  I expect revolutionary Communists to look more like the UK’s Corbynistas. 

What I do know, given Mélenchon’s policies mentioned above, is that they would drive even more of France’s entrepreneurial families to London, where they remain most welcome. 

My hunch is that the youthful, fresh faced former banker Macron will win, now that he has positioned himself at the political centre of French politics. 

However, if Le Pen or particularly Mélenchon becomes the next president of France, that should make the UK’s Brexit a little easier.