Today’s newspapers do not make good reading for the prime minister. “Europe gives you cancer!” says the Express. “Europe to slash house prices!” says the Mail. “Katie Price has huge breasts!” says the Star. I was in a bit of a hurry this morning so I cannot vouch for the complete accuracy of the headlines, but I hope you get the drift.

David Cameron will inform the House of Commons today about the negotiations he has been having with the EU over reforms. So far as I can see, he has come back with virtually no concessions, so his appearance in parliament should be toe-curling. His backbenchers – and indeed some frontbenchers – will be scenting blood today, Cameron’s blood. It is the job of Labour in particular and Jeremy Corbyn in particular to exploit the divisions in the Tory Party and in so doing repair the divisions in his own. I see today as being a seminal moment in Corbyn’s leadership.

The Mail, owned by a non dom who lives in France, and the Sun, owned by a naturalised American who used to be Australian are the most popular newspapers in the land. It will be grim reading today because these papers, and others, are condemning his reforms unreservedly today. Make no mistake: they are throwing their weight behind England leaving the EU and if we vote no on 23 June that’s what will happen.

I say England because Scotland will vote yes and will demand another referendum on separation and this time will win it. Wales could go the same way. What would the implications be for Northern Ireland? It would be the end of the UK as we know it. Just imagine it: the dissolution of the UK brought about by the Conservative and Unionist Party.

Leaving the EU would be a potential disaster for the UK, with the potential loss of jobs and trading partners through being outside Europe’s free market. Within days of a no vote many economists believe our economy would instantly tank, sending us into recession. Even little things like going on holiday to EU areas could become far more complex, never mind working there.

Which is where Jeremy Corbyn comes in. Today, he will need to be John Smith, Robin Cook and, yes, Tony Blair all at the same time. Cameron is a sitting duck of a target, sitting in front of and alongside a large number of Tories who loathe Europe and have, finally, got their chance to sink the knife into Cameron’s back and front. He will need to be forensic, ruthless and passionate in ways we have never seen before. This is Corbyn’s Waterloo. He must take apart Cameron’s flimsy arguments, his minimal ‘achievements’ and exploit Tory divisions. This is a golden opportunity for Labour’s new leader and he must take it if he wants to persuade an unpersuaded electorate of his PM potential. One big set piece could change everyone’s perceptions of him.

Forget the media because they will always hate Johnny Foreigner, but people who work in engineering, finance and what’s left of manufacturing will understand the catastrophe Brexit would have on their lives and jobs.

Put simply, Cameron is on the ropes. Today Labour and Corbyn must keep him there and go for the knockout. What a golden opportunity.