First, when it comes to Brexit, there are the familiar problems. On EU law, the prime minister’s idea is to pass a "Great Repeal Bill" to take effect the day we leave. This will do exactly the opposite of what its title suggests: it will confirm the place of every existing EU law in the UK statute books, at least initially. The idea is that Parliament will then go through and review them all over the coming decades.

Even this supposedly most straightforward of steps is riddled with complexity. EU laws in the form of shared regulations lay down cross-border protections for consumers, as well as technical and legal standards enabling products to circulate without further ado. But then what happens when EU countries decide to amend a regulation a few months or years down the line? Do we meekly accept decisions over which we no longer have any say, like Norway, and change our rules too? Or do we allow our rules to drift away from their continental counterparts, thus making technical standards no longer compatible, nullifying consumer guarantees and progressively shutting us out of the single market on which so much British trade depends?

But while the dangers of quitting not just the EU, but the single market and the European customs union as well, are now widely discussed, there is more that we are yet to consider. Soon, though it will be hard to ignore. Over the years, we’ve taken advantage of the EU framework in many practical ways to help us achieve many national objectives. Unpicking each of those is its own bureaucratic nightmare.

For a start, we save money and administrative headaches by doing tasks jointly rather than duplicating each other's effort many times over. Research is the classic example. There’s simply no point in every single country paying for its own expensive medical research, for instance, when collaboration brings better results faster and far more cheaply. In recent years, this joint approach has made Europe a world leader in science and Britain an internationally recognised centre of excellence. Are we really ready to pay an entire continent’s worth of investment out of our own national coffers, simply to try and keep pace with our neighbours?

Then there are areas where we have world-level international commitments to meet, whether we like it or not. Right now, as an EU member, we often delegate compliance to joint agencies. To take just one example: currently we take care of our international reporting and monitoring obligations on maritime safety through our membership of the European Marine Safety Agency (EMSA), and through shared EU rules on seafarer working conditions. This is how we maintain Britain’s status as a "quality flag state" under international law. If we lose this, we don’t lose our obligations — but we do lose our ability to meet them quickly and easily. Will we set up a separate UK agency for this purpose? Where will we find the necessary expertise, how long will it take and what will it cost?

Similar points apply to a whole host of fields. How will we certify aircraft, their engines and other related products for safety if we leave the European Air Safety Agency? How about approving medicines for sale on the market, currently done through the European Medicines Agency based in London? How about testing and authorising (or banning) potentially hazardous chemicals, currently done jointly through the European Chemicals Agency? Responding to coastal pollution (European Environment Agency)? Protecting British trademarks and patents abroad (European Union Intellectual Property Office and the Patent office and court)? Ensuring that our sat-nav systems work (European Global Navigation Satellite Systems Agency)?

The list of agencies whose work we would suddenly have to duplicate is very long. And every single case will need its own, bespoke, solution.

Finally, there are areas where we co-operate because there are things we can’t do alone, as a simple matter of logic. It’s futile to make unilateral attempts to manage local fish stocks, for instance, when fish have the unfortunate habit of swimming from one country’s territory to another’s. We can’t possibly maintain our open skies agreement across Europe, vital to so many UK businesses, without the cooperation of other countries. And the European Arrest Warrant, which has both brought homegrown crooks back to face British justice and allowed us to remove foreign ne’er-do-wells from British soil in days rather than decades, simply could not exist without the shared legal frameworks we’ve developed with our neighbours.

In all these areas and many more, the point is not that pulling out of the EU means throwing in the towel. Quite the opposite. We will still need to find ways to do these things, either because of blatant self-interest or because of our wider commitments to the world. Other non-EU members do them too. But once we’ve lost our EU membership, we will have the worst of both worlds. We’ll incur massive economic and bureaucratic costs – the kind of costs we’ve spent the last fifty years gradually eliminating — at the same time as crippling our effectiveness both domestically and on the world stage. At best, we will have to find new and potentially complex ways to continue the cooperation which, inside the EU, has been straightforward. At worst, we will simply have to duplicate everything.

It’s all too easy, as Britain is now discovering, to decide one day to quit the EU. But managing the fallout from that decision is a bureaucratic and costly nightmare, and getting Britain back on its feet post-Brexit will be a Herculean task.

Britain in Europe has led the world in so many areas. It seems likely that only through dismantling that leadership will we realise quite how good we’ve had it up till now. When reality hits home, it will hardly be surprising if we see people asking for a rethink of the Brexit decision.

Richard Corbett is the Labour MEP for Yorkshire & Humber.