Ireland cannot afford to drag its feet on sorting out Border
Disengaging the UK from the EU will be like undoing all the stitching of a patchwork quilt and then restitching some parts of the quilt together, while making a new quilt of the rest.
The UK is, at the moment, stitched into thousands of regulations and international treaties, which it made as a member of the EU over the last 43 years.
Each piece of stitching will have to be reviewed, both on its own merits and for the effect that rearranging it might have on other parts of the quilt.
This is, first and foremost, a problem for the UK itself.
We all think we know what UK voters voted against on 23 June. But nobody, even in the Conservative government itself, has a clear idea what UK voters voted for.
People voted to leave the EU for contradictory reasons. Many voted to leave because they wanted more protection from global competition.
On the other hand, many of the Leave campaign leaders wanted to get out of the EU so they could deregulate their economy, dispense with EU social rights and promote more global competition and lower costs (wages) in the UK economy.
The UK government must first decide which of these economic policies it wants. Only when it has done that, can it decide what sort of relationship it wants with the EU.
The 27 EU heads of government told the UK on June 29 that any trade agreement would be concluded with it "as a third country".
This could be interpreted as meaning that the UK must first become a 'third country' by withdrawing from the EU, before it can have a trade agreement with the EU. This could mean that the UK would have to be out of the EU before it knew what terms it might get on trade. This would be a very hardline EU position.
If that is what the 27 leaders meant, it is probably contrary to Article 50 of the Lisbon Treaty, which says a withdrawal treaty must take account of the "framework" of the withdrawing country's "future relationship" with the EU.
I believe Article 50 means that there will be two negotiations, one on 'withdrawal' and one on the 'framework' of the future relationship.
Furthermore, I believe the two treaties must be negotiated simultaneously and in parallel, and that the framework agreement cannot wait until the UK is already a 'third country', as seemed to be implied by the 27 leaders .
Ireland cannot afford to wait until the UK is already a 'third country' before border, travel, and residency issues between Ireland and the UK are sorted out.
We need to have these issues sorted out before the UK leaves.
As with a divorce, the withdrawal treaty will be about dividing up the property. It may be easy enough to negotiate.
The Framework Treaty will be about the future and, like marital disputes about access to and care for children, will prove to be much more fraught and complex.
The question of whether there is a 'hard' border or not will flow from what the UK looks for, and what it gets, in its framework negotiations.
Nobody knows yet what the UK will look for, so this question is impossible to answer. The 27 EU leaders rightly insisted that the four freedoms - of movement of people, goods, capital and services - go together. Nobody has any idea yet how the UK will propose to get around that.
If the UK was to heed the call of Liam Fox, the new Minister for International Trade, for it to leave the EU Customs Union, in order that it could negotiate trade agreements with countries outside the EU, this would mean an immediate hard border in Ireland.
The Taoiseach's diplomacy in recent days has probably helped to head off that threat.
Implementing Mr Fox's proposal would have breached a UK Treaty obligation, which is a very serious matter for a country that relies on 30,000 international treaties. The sort of border we have in Ireland will depend on the shape of the final UK/EU Framework agreement on all of the four freedoms. Ireland can do no side deal with the UK.
And if Ireland is to influence the EU positions in its favour, it has to present its case as being beneficial to Europe as a whole.
It cannot be, or be seen to be, on both sides of the table at the same time in what will prove to be a highly contentious negotiation.
Until it leaves, the UK is still a member of the EU and is bound by all the rules. It will fully participate in all key EU decisions, except those concerning its own exit terms.
This means that the UK cannot do trade deals with other countries, while it is still in the EU.
Indeed, it would appear that it cannot even enter into commitments about future deals, particularly ones that might undercut EU negotiating positions.
This is because, as long as it is still an EU member, the UK must, under Article 4 of the Treaty, act in "sincere co-operation" with its EU partners. The meaning of "sincere co-operation" was elaborated by the European Court in judgments it made on cases that the Commission took against Germany and Greece to overturn separate understandings that each had forged with other countries on matters that were EU responsibilities without EU involvement.
So to ensure that he stays within the law, Liam Fox may have to take a Commission official with him on all his trade travels around the globe, at least until the UK has finally left the European Union.
Indeed, the more closely the UK government looks at its options, the longer it may take to decide when to trigger Article 50.
The leaders of the EU 27 should not rush the UK on this. Short-term uncertainty is a very small price to pay for avoiding a botched and ill-prepared exit negotiation. Everyone would lose from that.
The UK civil service did not, after all, expect to find itself in this position. Indeed, UK civil service studies, done long before the referendum, concluded that the UK's then existing relationship with the EU was just about right.
Furthermore, once Article 50 is triggered, the UK cannot, easily or legally, change its mind and revert to the status quo, even after a General Election.
Meanwhile, Europe, with so much other work to do, has to turn inwards and devote itself to unravelling 43 years of interweaving between Britain and Europe. All this highly demanding technical work has to be done, at a time when Europe should be looking outwards towards the opportunities and threats of a rapidly changing and unstable world.