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Perhaps the greatest fallacy in the UK's Brexit referendum was that there was a viable way to leave the European Union.

Each side in the campaign had its own reasons for wanting to ignore the fact that the process set out under Article 50 of the Lisbon Treaty was at best vague, at worst unfeasible.

Of course the word 'viable' carries a lot of weight in this. But Article 50 set an unrealistic timescale (two years) and an unworkable condition, that the leaving country could not even start to negotiate its future trading relationship with the bloc until it was out.

When Cecelia Malmstrom, the trade commissioner, confirmed in a Newsnight interview just days after the referendum that the understanding of the EU's bureaucrats was precisely this, it caused consternation in many quarters.

The Lisbon Treaty's vague assurance that the withdrawal agreement would contain some phrases about the future relationship just compounded this issue rather than resolving it.

Extensions to transition?

British politicians wanted the 'future relationship' clauses to include defining the new trading arrangement; people in the Commission were absolutely determined that it shouldn't go beyond vague statements of principle. And that's where we still are today, more than two years on.

Article 50's 'ticking clock' put a loaded gun to everybody's head by stating that if there was no agreement during its strict 24-month negotiating timescale, the UK would simply cease to be a member in March 2019, and default to the direst of trading terms.

Of course the negotiations have delivered some progress but in many areas that just tends to underline the point that Article 50 wasn't viable, rather than undermine it.

In order to bridge the gap between leaving and defining the new relationship, a transition phase was agreed. But few people involved in the talks believe that this 20 month extension will be long enough to define a new relationship.

There is every possibility that in order to avoid a new 'cliff edge' at the end of the transition, extensions will be needed and that Britons who voted for Brexit will not see its shape fully defined until five, six, who knows how many, years after the referendum.

So whatever happens (and, of course, the UK has not actually left the EU yet), the emergence of one or more 'transition' extensions has already demonstrated that Article 50, as written, was never workable.

Leave campaigners, even if they had anticipated this, did not want to tell people, back in 2016, just what a long, complex and uncertain process this would be.

Deliberately difficult

Remainers, for their part, preferred to avoid engaging with the idea that Article 50 was accepted into the Lisbon Treaty on sufferance by European leaders who by and large did not believe it was desirable or possible to reverse a generation's worth of integration.

Imagine campaigning on a platform that we were better off in because actually nobody knew for sure that it was possible to get out.

Jeremy Hunt received widespread condemnation for his Conservative party conference suggestion that there were parallels between the EU and the Soviet Union. It was particularly offensive to people in the Baltic republics, with their bitter memories of living under communism.

But in my view, there is a single point of valid comparison. And it comes in the way treaties are drafted.

The Soviet constitution contained Article 72, which stated, "each Republic shall retain the right freely to secede from the USSR".

It was never meant to be used, of course, and some have argued that in its failure to give any description of the mechanism for leaving, it communicated that brutal fact rather more clearly than the EU's Article 50.

We are left with negotiators struggling to avoid the 'cliff edge' created by Article 50's combination of a refusal to talk trade until you're out, and an aggressive timescale for negotiation of a withdrawal agreement.

It's a mess, and it comes from politicians agreeing all those years ago to Article 50 in a spirit that it should never be used.

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