If the UK votes to ‘Brexit’ on 23 June, it is impossible to comment at this stage on what becomes of the 3 million or so EU nationals living in the UK and also of the estimated 2.2 million British nationals living in other EU countries (with reportedly nearly half enjoying the sunshine and sangria in Spain – guess who will not be voting to Brexit on 23 June?).

This is because no one really knows – or can know – at this stage. No one has ever done this before.  There are a few things, however, that can be said, with relative authority.

Firstly, in the event of an ‘out’ vote, nothing will happen overnight.  Article 50 of the EU’s Lisbon Treaty sets out the procedure to be followed if a country wishes to leave the EU.  The terms of the withdrawal will need to be negotiated, with Britain on one side of the bargaining table and all the remaining 27 members on the other. If a deal is to be made, both sides need to agree.  From those on the other side of the table, this requires support from a so-called ‘super qualified majority’, i.e. at least 72 per cent of the 27 continuing members, representing at least 65 per cent of their population and from the European Parliament.  If no deal is made within 2 years, the UK’s membership will automatically expire, unless a further extension period is unanimously voted for by all the other 27 members.

The idea of a second referendum is also being put forward, based on terms of the withdrawal agreed at the negotiating stage. That does create the humiliating prospect of the UK population rejecting not only continued EU membership but also the terms of ending it – meaning what? That we go back in again? Just think of the damage to personal and business confidence that prospect would do. Given the huge complexity of any withdrawal, however, it does not take much to predict that the negotiations will be long and protracted and an extension in time beyond the two years may well be necessary.

Current popularist sentiment within the UK regarding the number of immigrants coming into the country may mean that the continued free movement of people coming to the UK from other parts of Europe is a red line in any negotiations. It is possible to say that were it not for that issue no one would be thinking seriously about any of this in the first place. It may be that the argument of the benefits of the free market to UK businesses prevails but if a looser trading arrangement is negotiated and freedom of movement to the UK is no longer part of the arrangement, then we start to see some quite serious levels of concern about any transition out of EU, with some predicting it to be a “bloody nightmare” and a “bureaucratic crisis”.  And what then of the 3 million EU citizens living  in the UK, often with non-EU family members?

It is difficult to predict if a particular date will determine eligibility to remain in the UK and what that date may be. If any future date (e.g. physical residency in the UK on X date) is put forward, it may trigger a possible Daily Mail nightmare-type ‘stampede’ to the UK (and also out of the UK to Spain, for example). A more plausible approach may be that any EEA national lawfully residing in the UK at a past date – at the date of the referendum, for example – who is working, studying (broadly anything over and above being merely just a visitor) will be permitted to stay in the UK, with any new rules applying to new arrivals only.

The chances of vast numbers of EU nationals currently living in the UK being required to leave their jobs, homes and withdraw their children from schools are vanishingly slim. Even the least well-informed members of this debate will probably recognise that that you can’t pick and choose among EU nationalities for this purpose, and that if you make a decision requiring the withdrawal of some, you will therefore lose all, despite the devastating impact that would have on business, the City, the arts, sport, leisure and basic social services. A quick Google search reveals, for example, that the Premier League alone contains far more foreign players than locals. Including 35 from France, 32 from Spain, 22 from Holland, 19 from Eire, 18 from Belgium, 8 from Germany, 7 Italians and 5 each from Serbia and Portugal.  Leaving the EU is one thing but I cannot see there being any public appetite to take that to its logical conclusion so far as immigration status is concerned.

So we can tentatively conclude that in the event of any Brexit, all will become apparent only after a protracted series of negotiations that may take years. And this means that, in essence, those who vote ‘out’ will not really know what they are voting for, which is quite a scary thought.