David Cameron insists that he didn’t say it.  The lobby insists that he did.  And the facts of the matter are not on the Prime Minister’s side.  Ministers aren’t sent on to the Today Programme to defend the Government’s position unless so instructed. We can therefore be sure that when James Wharton went on it yesterday, and said that Ministers who back a No vote will have to resign during the referendum campaign if the Government backs a Yes vote, he was saying what he had been told to say.  (Welcome to the happy world of collective responsibility, James.)

In any event, Wharton was merely restating Cameron’s known position.  As Tim Shipman pointed out yesterday, the latter first set it out to Conservative members of the Cabinet in 2012.  There is a threefold logic to his view.

First, it’s a bad thing for political parties to be seen to be divided.  Were Conservative Cabinet members to go in different directions during the campaign while Labour’s Shadow Cabinet members held together, voters would draw the obvious conclusion.

Second, resignations before it begins would liberate the Prime Minister from those Cabinet members he doubtless regards as Eurosceptic extremists – a gain which might be worth the publicity pain of their resignations, at least from his point of view.

Third, resignations would tilt the balance of the Cabinet and Government broadly from the right to the centre – and forcing a choice might keep them to a minimum.  The Conservative Party would thus move closer to where Cameron thinks voters want it and believes that it should be.

This take is all very well in theory, but it won’t work in practice.  Both the main political parties have differences on EU, but the Conservatives’ run deeper than Labour’s.  Like the fissures over protection during the 1840s or the early period of the last century, Europe has party-splitting potential.

The Prime Minister doesn’t want to go down in history as a Robert Peel.  His plan for a renegotiation and a referendum was devised precisely to avoid him meeting that fate.  So if he is to stick to it, he must continue what he started.

This means “doing a Wilson”, and allowing Cabinet members who differ from him on Europe to go their own way during the campaign itself – or, at the very least, step down from government for a few weeks on the publicly guaranteed basis of a return afterwards in the event of a Yes vote.

The lesson of yesterday’s events is that Cameron will be compelled down this route in any event.  If he can’t hold his line for 24 hours, with the referendum still at least a year away, he won’t be able to hold it for longer next year or the year after, with the vote on his doorstep.

Better by far to give Michael Gove, Iain Duncan Smith and Chris Grayling (not to mention Sajid Javid, John Whittingdale, Priti Patel, Michael Fallon, Justine Greening, Theresa Villiers, and other members of the Cabinet of a strong Eurosceptic bent) their freedom now than be seen to be forced to do it later.

The Prime Minister could instead seek to hold a reshuffle next summer, and purge as many of his strong Eurosceptics from the Government as possible – getting them out of the way before the referendum.

But this would be a risky course, given his majority of only 12.  It would also unravel the progress he has made since the election in bringing the Parliamentary Party together and healing the wounds of the last Parliament.

Even now, yesterday’s events have put that progress at risk.  They have also taken the shine off the effective launch today of the EU Referendum Bill in the Commons, about which Phillip Hammond writes on this site.

All in all, we believe that Cameron should give ground to his more Eurosceptic colleagues – but also that, in return, they should give him something back.  Ministers who want to campaign for Out shouldn’t be compelled to leave the Government.  But the Prime Minister shouldn’t be forced to undertake a fundamental renegotiation that goes further than he wants, and for which there is no basis in the manifesto on which he won an election only a few weeks ago.  Who knows, such a Grand Bargain might even spark an outbreak of Tory unity on Europe – an outcome devoutly to be wished…