Brexit will be “done” by 31 January, except little will change. What the Brexiteers have mistaken for a single moment will in reality be a lengthy and painful process. In most policy areas shaped by EU influence, post-Brexit changes will be slow and incremental. There is, however, one exception to this rule: immigration.

After 1 January 2021, free movement will end and EU and non-EU citizens wishing to move to the UK will (unless they are Irish citizens) be treated the same. Despite this shake-up, it’s still unclear what Britain’s new immigration system will look like.

When Boris Johnson and Priti Patel promised an “Australian-style points system” last year, their plans were largely vacuous. The Conservative government subsequently commissioned the independent Migration Advisory Committee (MAC) to advise on the shape that Britain’s future immigration system should take. Johnson and Patel probably didn’t expect the MAC’s outgoing chair, Professor Alan Manning, to dismiss talk of their Australian-style points system as, aptly, “pointless”. For good measure, the report also notes that the UK has far more to learn from Austria – where skilled migrants are generally required to have a job offer – than it does from Australia, where many are not.

Whether or not the MAC recommendations are adopted in full, big changes are on the way. Theresa May’s 2018 white paper recommended a salary threshold of £30,000 for skilled migrants with a job offer. Businesses – in sectors such as fashion, technology and research, all of which employ EU nationals who, while far from unskilled, earn less than £30,000 – argued for a reduced threshold of £20,000 or £22,000. The MAC report has split the difference, proposing a £25,600 threshold, higher in some better-paid occupations, with special rules applying to NHS and education sectors. Crucially, the report also argues that if the government really wants to adopt a “points-based system” for the most highly skilled migrants, it will need to be far more flexible about the sorts of people it admits – and recognise that not everyone who arrives in Britain will succeed, at least not necessarily in material terms.

These proposals should please businesses, although some in lower-paying sectors such as hospitality and food processing, especially outside London, will still face a big shock. The NHS should be able to live with the new arrangements, which essentially say that not just doctors and nurses, but people working in lower-paid positions, will be eligible under the new rules. It will be far harder for social care to adapt to the changes, where the MAC – as it did in its last major report – argues that the problem is that care workers aren’t paid enough because the care system has been persistently underfunded and that the government shouldn’t use immigration as a way of dodging these issues. Their point is valid but it will be of little comfort to those who rely on Britain’s care system now.

All this will amount to rapid change. There will need to be consultation, particularly with employers, if not on the big decisions then on a host of second-order questions; and then there will need to be time for business to get used to the new system, which will be considerably more costly and burdensome than freedom of movement.

For many employers that depend on immigrant workers from the EU, and therefore don’t need to interact with the immigration system at all under the current arrangements, this is not simply a matter of extending and tweaking existing processes and procedures. Businesses (particularly small ones) will suddenly find there are Home Office forms to fill in, fees to pay, and time-consuming bureaucracy to navigate. Time is short – by the summer, employers will want to know what to say when making job offers to EU nationals. The most important immediate impact of Brexit for business will be lots more red tape.

So will post-Brexit Britain, without free movement, become closed to all except the “brightest and best”, vindicating Brexiteers who voted to restrict immigration and slow the pace of demographic and social change? Or will we move into a new era, in which global Britain will benefit from skills and talent from all over the world, rather than simply sucking in cheap labour from the rest of Europe?

The answer is likely to be somewhere in between. What is certain is that these proposals are far more liberal than anything we could have expected from Theresa May. Immigration-bashers and nativists in the Conservative party and beyond will find this uncomfortable – particularly the resulting increase in immigration from outside the EU. But immigration is a less salient issue among the electorate than it was in 2016, and public perceptions of the economic and social impact of immigration on the UK are far more positive than they were at the time of the referendum. For some people, at least, ending freedom of movement - and hence restoring “control” over immigration - may be more important than guaranteeing lower numbers of migrants.

So there are grounds for at least cautious optimism. Contrary to the hopes and fears of many, Brexit looks less like it will make a decisive turn towards restricting immigration. Instead, consistent with the more benign aspects of our history, it may signal a different form of openness.

• Jonathan Portes is professor of economics and public policy at King’s College London, and is a senior fellow at UK in a Changing Europe