‘Second vote might be the life raft the Conservatives need to stay together’ says Vernon Bogdanor

Because the victory was so narrow, there has been ‘an unstoppable demand for a re-run’.

‘Win or lose this battle, we will win this war’ – these statements were made not by Remoaners after the referendum, but by Nigel Farage five weeks before it when he feared that he would be defeated.

But Farage was right. A referendum exemplifies the principle of the sovereignty of the people which, on the European issue, is held to trump the sovereignty of parliament. But, just as the sovereignty of parliament means that Parliament can always change its mind and cannot be bound by its previous decisions; so also the sovereignty of the people means that the people can always change their mind and are not to be bound by their previous decisions. As David Davis, the Brexit Secretary, has said: ‘If a democracy cannot change its mind, it ceases to be a democracy.’

The British people voted for Brexit for two reasons. The first was that they wanted to limit immigration from the EU. The second was that they wanted to ‘restore control’, to ensure that laws were made domestically and not by the EU.

But what was not clear was whether they were prepared to pursue these aims at the expense of their standard of living and if so, how much of a reduction in their standard of living they would be willing to accept. The voters were in the position of someone who sees a nice house by the sea that they would like to buy, and is then asked to make a decision on purchasing it without knowing the price.

There is of course nothing inconsistent in accepting a reduction in one’s standard of living in order to achieve some other desirable aim.

That, after all, was what the Irish did in 1921 when they won their independence from Britain. They knew, surely, that their standard of living as an independent country would be lower than if they remained in the United Kingdom. But they believed that independence was well worth the price. The same, of course, was true of the ex-colonies which achieved independence.

But we do not yet know what the cost of Brexit will be, nor whether the British people are prepared to pay it. That in essence is the case for a second referendum – or, to be more precise, for a referendum on the outlines of the deal agreed between Britain and the EU.

The position of the British Government is clear. It proposes to leave the customs union and the internal market, but to seek a free trade agreement with the EU – hopefully a bespoke agreement, tailored to British needs.

When the outlines of the free trade agreement become clearer, the economic cost will also become clearer. We will then know how much we have to pay for the nice house by the sea.

If, as seems likely, Brexit raises costs in terms of non-tariff barriers for industrial and financial institutions, that could lead to them locating abroad and a consequent loss of jobs. Those who might lose their jobs as a result have a right, surely, to a say on whether they wish to proceed.

The Government of course is hostile to a further referendum, even though the majority of the Cabinet and around 50% of Conservative MPs supported Remain. The Government argues that Article 50, by which Brussels was notified that Britain will leave the EU by the end of March 2019, is irrevocable.

I am sure that this view is mistaken. Invoking Article 50 initiates a negotiation, and a member state can, at any point, decide that it does not wish to continue with the negotiation. If I negotiate to buy a house, I am not committed until the contract has been signed. I can always withdraw if I find that the house is in worse condition than I had imagined, or that I can no longer afford to pay for it.

If a state were unable to revoke its notification when it had genuinely changed its mind, perhaps after a referendum, the consequence would be that it would have to complete the withdrawal process, sign a withdrawal agreement, and then re-apply to join under the provisions of Article 49.

That would be absurd and indeed quite contrary to the spirit of Article 50, which is intended to provide for a negotiation, not for the expulsion of a member state that wishes to remain in the EU.

Constitutionally, therefore, a change of mind is perfectly possible. And politically, it would be a grave mistake to exclude a further referendum from consideration. Indeed, it could be in the Government’s own interest to hold one to secure legitimacy for its deal with the EU.

For the deal is likely to be far less favourable than ministers fondly imagine.

If one resigns from a tennis club because one does not wish to pay the subscription and does not like the rules, but wishes to continue to use the courts, one is not in a strong position. Certainly one is unlikely to be able to play tennis on the same basis as the members. It will not be easy, therefore, to sell the agreement to the country as the best available. If, as is likely, the agreement is disadvantageous, the public might ask what has happened to the £350m a week that was promised for the National Health Service. That will not be an easy question to answer.

In addition, there may well not be a majority in Parliament for the deal that the Government finally secures. The Labour opposition is bound to say that it would have secured a better deal. The Liberal Democrats will argue for a referendum. The Conservatives are likely to be split. The extreme Brexiteers will accuse the Government of appeasement, of handing over too much money to Brussels and accepting too many restrictions on Britain’s freedom of action. The Remainers will say that the Government should have negotiated a closer relationship with the EU, involving perhaps continued membership of the internal market.

The Conservatives are, after all, the party of business and finance, and these interests are likely to be deeply concerned if, almost uniquely in Europe, Britain has no more than a free trade agreement with the EU.

Twice before, Prime Ministers have sought to avoid a split in their ranks on Europe by calling a referendum – Harold Wilson in 1975 and David Cameron in 2016.

Both were criticised by purists, but they did succeed, in the short run at least, in holding their parties together. In 2016, voters rejected advice to remain in the EU. But in 1975, voters accepted advice to remain in the EU, and that gave legitimacy to Britain’s membership. An adviser to Harold Wilson commented that, while Edward Heath had taken the British establishment into Europe, it had needed Wilson to take the British people into Europe.

A referendum on Europe was first proposed by Tony Benn to Labour’s National Executive in 1971. He could not find a seconder. But James Callaghan shrewdly said that the referendum might prove ‘a rubber life-raft into which the whole party may one day have to climb’. Today, similarly, the Conservatives

might find that they need that life-raft if they are to hold their divided party together.

Vernon Bogdanor is Professor of Government at King’s College, London. His books include The New British Constitution.