The great constitutionalist and jurist AV Dicey (1835-1922) regarded the referendum as a popular defence against the follies of the political class. It was “the people’s veto; the nation is sovereign and may well decree that the constitution shall not be changed without the direct sanction of the nation”.

Dicey’s intellectual heirs insist that the encroachments of Brussels bureaucracy and European law since the 1975 referendum on EEC membership have been so great that the people have long been owed fresh consultation. And, to an extent, David Cameron and George Osborne agree with this analysis.

The EU constitutional treaty and its successor, the Lisbon treaty, “let the referendum genie out of the bottle” (to use the chancellor’s private image), and set the PM on course to his declaration in the Bloomberg speech of January 2013 in which he pledged an in/out referendum before the end of 2017.

It has long been an article of faith for Cameron that the Tories did themselves no electoral favours by “banging on” about Europe. When they should have been talking about education, health and welfare, they were arguing about how many Bill Cashes can dance on the head of a pin. “Banging on” about the EU also drew attention to the splits within the party, initially between Europhiles and Eurosceptics; and, more recently, between Eurosceptics who want to stay in the EU and Eurosceptics who favour outright “Brexit”.

Today’s announcement by the PM that ministers will be freed from the obligations of collective responsibility during the referendum campaign is the product of practical politics rather than high principle. In 1970, Jim Callaghan foresaw that the referendum on EEC membership was “a little rubber life raft into which the whole party may one day have to climb”. Thus, in 1975, Callaghan himself, Roy Jenkins and Denis Healey campaigned for a yes vote, while Michael Foot and Tony Benn called for Britain to terminate its association with the common market.

Cameron and his inner circle certainly considered the option of insisting upon a single party line during the forthcoming referendum. But not for long. Chris Grayling, leader of the House of Commons, made clear to the PM that he could not stay in the cabinet if such arrangements were imposed upon ministers.

Iain Duncan Smith, the work and pensions secretary, and Theresa Villiers, at Northern Ireland, would have faced a similar predicament as advocates of Brexit in high office.

Yet the real problem was – and is – the core of senior Tories who have kept their options open while Cameron has flown around the continent seeking concessions. It is a formidable list: Theresa May, Michael Gove, Boris Johnson, Oliver Letwin, Sajid Javid, Justine Greening, John Whittingdale, Priti Patel and others. Conscious of the stakes, these politicians have hugged their cards close to their chests. Cameron faces the prospect that all – or many – of them will decide to back Brexit when the PM’s negotiation is complete.

That is bad enough (assuming that Cameron does not shock us all by opting for exit himself).

To impose collective responsibility upon ministers would have been to court disaster, a mass resignation that few governments can survive. Imagine the political neuralgia if Cameron and Osborne find themselves pitted against Boris in the debate. How much worse it would be if the mayor were defying his obligation as a member of the political cabinet. Better to suspend those obligations, duck as much shrapnel as possible, and pick up the pieces afterwards.

So is Cameron out of the woods? By no means. Bear in mind that today’s announcement is a damage limitation exercise, and no more. In principle, it means that the Conservative party can resume its governing role after the vote is held, freshly reunited and seamlessly harmonious. Of course, the aftermath will be very different, the scene battle-torn and bloody, and many of the scars will be livid for years. Just as the 1975 referendum paved the way to the split between the Labour left and the SDP, so the forthcoming EU vote will create as many problems as it resolves, bleeding (for instance) into the leadership contest that must take place before the general election in 2020.

The timing of today’s announcement suggests that Cameron does indeed plan to conclude negotiations in February and to hold the referendum sooner rather than later. He hopes for a swift victory, the rapid resumption of business as usual, and the entrenchment of Osborne’s position as the favourite to succeed him. But what if he loses? Can a prime minister survive such a defeat? To that, there is no formal answer – only the rough rules of practical politics.

And what if Boris decides to take a leading position in the Brexit campaign and helps that campaign prevail? Who then will be in pole position? Today the PM is doing all he can to minimise the risks inherent in this referendum. What lies ahead of him hereafter is uniformly perilous.