We’ve come a long way since the referendum, more than a year and a half ago (23 June 2016). We know more today than we did then. We know that leaving the EU is not a simple matter of cancelling a club membership but a very complicated business with consequences for all aspects of national life. We know that it will take more time than then envisaged so that a “transition period” of perhaps two years has been agreed after the date of formal exit.

If the decision were to be made today, it would be made on the basis of knowledge that we did not have then. A referendum today might still have had the same outcome, or it might not, we cannot know.

When we get into the spring of next year, we will know more again. We should then know more about the relationship between Britain and the EU when/if Britain leaves. Someone will then have to judge whether it is then in Britain’s best interest to leave, knowing what we then know. What that someone will then conclude we cannot know now – but someone will have to make the judgement.

That someone is Parliament. MPs may or may not like it, but it will be Parliament’s burden to judge what is in the nation’s interest, the facts being what they will then be. The referendum notwithstanding, leaving or not will be Parliament’s decision.

If Parliament were to decide that Britain should not leave the EU, would that be undemocratic, given the 2016 referendum? The answer is, no. Parliament is the supreme authority in Britain’s democracy and the custodian of the nation’s well-being. It was Parliament that triggered Article 50 of the EU Treaty (on 29 march 2017), and it is Parliament that must decide what is best at the end of the negotiation process, on the basis of the facts as they will be then. It is standard for Parliament to change its mind. If a law has been passed that turns out to work poorly, Parliament will change it. That is not “undemocratic” just because the original law was passed democratically.

If Parliament at that time were to conclude that it would be best for the country to change its mind, it is possible that it will call another referendum. That would not be necessary for democratic reasons – it is in Parliament’s authority to decide – but Parliament might for political reasons see no other way.

What judgement Parliament will make in a year’s time, we cannot know. But Parliament is well aware of the burden it carries in having to make the judgement. This is being worked on in Parliament day in and day out. The action leading up to the final decision is and will be in Parliament.

Parliament’s final judgement will depend on the facts as they will then be known. The ongoing debate matters but the facts will decide. We are already seeing that changing facts result in changing constellations in Parliament. There is now a majority in Parliament for a deal in which Britain remains within a custom union with the EU.

My guess is that Parliament in a year’s time will decide that it will be best for Britain to remain a member of the EU. It will turn out that leaving will be too costly, in six ways:

  1. It will be too costly economically. The EU gives Britain seamless trade and economic collaboration with its biggest and most important markets. Introducing impediments on that trade and collaboration will bring burdens onto Britain’s economy.
  2. It will be too costly in terms of other collaborations, such as in science, education, health care, security, culture and more. It will be costly for Britain to make itself a second-class partner in collaboration.
  3. It will be too costly in terms of risks to Britain’s own union. Brexit will give the nationalists in Scotland the arguments they need to push through independence. A division of some kind of border will re-emerge between Northern Ireland and Ireland. The Irish settlement will be put in danger and the question of all-Ireland unification will return to the agenda.
  4. It will be too costly for Britain’s standing in the world. Britain on its own will be a small country in a big world, without much influence. Europe unified is a world power. By leaving the EU, Britain gives up the clout is has as a partner in the European block.
  5. It will be too costly in terms of the younger generations’ future. The European lifestyle of mobility, multi-nationality and borderless living in education and work will be made less available to young people in Britain.
  6. It will be too costly in terms of the damage imposed on friends in Europe. The European Union is a political project. The aim is to transform Europe from a continent in enmity to one of nations tied together in the security of bonds of collaboration. By turning its back on this project, Britain does damage to a cause that matters deeply to friends on the continent.