When Theresa May was placed at the far end of a row for the G20 “family” photograph, it was interpreted as evidence that the UK was no longer regarded as a major global player following the vote to leave the EU. Yet positions in G20 photos reflect only how long a particular leader has been attending. May’s position on the periphery is explained by the fact that was her first G20 as UK Prime Minister.

When European Union leaders meet for what is described as an “informal summit” in Bratislava tomorrow Friday, however, the line-up will permit only one conclusion: the UK really will be on the periphery, or beyond.

The EU will be meeting at 27 – its new, post-Brexit, composition. The implications of the UK’s departure have dictated practically the whole agenda. But Theresa May will not be there; she has not been invited.

On the day after the EU referendum – a day distinguished by the absence of any party line, and therefore of spin – Philip Hammond was asked about future relations between the UK and the EU. He was then Foreign Secretary, and he answered (with unusual clarity) that the UK would no longer have a voice at the table. That was it.

Now Chancellor, he may be back to his customary circumspection. But the Bratislava summit is where the reality of Brexit will be driven home. The UK will not even be able to register its dissent by wielding a veto. Its views, one way or another, will simply not count. And it had better get used to it. The European Union wants, and needs, to start moving on.

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Two directions of further travel can already be discerned. The first is a desire to demonstrate that the UK cannot expect any special privileges. This is not about punishment, but about discouraging others from following where the UK has led. The choice of negotiators – Michel Barnier for the EU commission and Guy Vanderhofstadt for the European Parliament – and a host of declarations about there being no preconditions, but no prospect either of an EU “a la carte” either, sends this message unambiguously not just to the UK, but to the rest of the EU.

The second is an attempt to devise a serious new EU project, around which the 27 member states will be able to rally. This new project has begun to take shape and it is a defence and security alliance of the sort that the UK was always wary of.

From the alacrity with which the French and the Germans have announced preparations and the prominent place the plan occupied in Jean-Claude Juncker’s annual state of the EU speech this week, it could be deduced that UK resistance is what had been stopping such an arrangement all along.

21 maps and charts which will challenge perceptions of Europe Show all 21 1 /21 21 maps and charts which will challenge perceptions of Europe 21 maps and charts which will challenge perceptions of Europe Portugal drinks more wine than France Tindo - Fotolia 21 maps and charts which will challenge perceptions of Europe Young Italians, by some distance, are the most likely to live at home with their parents 21 maps and charts which will challenge perceptions of Europe Britain is on course to overtake Germany as Europe’s most populated country 21 maps and charts which will challenge perceptions of Europe Greek workers work the longest hours in the EU 21 maps and charts which will challenge perceptions of Europe Estonia has, per capita, more drug-related deaths than anyone else 21 maps and charts which will challenge perceptions of Europe The fastest download speeds are to be found in Romania 21 maps and charts which will challenge perceptions of Europe Slovenia, Malta and Poland have the smallest gender pay gaps 21 maps and charts which will challenge perceptions of Europe France hates its leader more than other European countries 21 maps and charts which will challenge perceptions of Europe Eastern and Western Europe are very divided on the issue of gay marriage 21 maps and charts which will challenge perceptions of Europe Germany has the most millionaires 21 maps and charts which will challenge perceptions of Europe Everyone likes Christmas, apart from France 21 maps and charts which will challenge perceptions of Europe Germany accepts by far the most asylum applications 21 maps and charts which will challenge perceptions of Europe The UK and France have some of the most positive views of Muslim people 21 maps and charts which will challenge perceptions of Europe Europe's largest Muslim population is in Germany 21 maps and charts which will challenge perceptions of Europe Danes are the most trusting Europeans, and Cypriots the least 21 maps and charts which will challenge perceptions of Europe Finland has the worst economy in the EU 21 maps and charts which will challenge perceptions of Europe Italy has cut back its military spending more than any other major European Nato member 21 maps and charts which will challenge perceptions of Europe Everyone is sad about the refugee crisis 21 maps and charts which will challenge perceptions of Europe People in Spain are also the most likely to live in flats (Brits are most likely to live in houses) 21 maps and charts which will challenge perceptions of Europe Spain is the most likely to feel neighbourly 21 maps and charts which will challenge perceptions of Europe Luxembourg is home to the highest proportion of foreign nationals

There is truth in this, but it is not the whole truth. What is true is that anything that even slightly hinted at the creation of a European defence headquarters was coldshouldered by the UK. London’s view was that any EU defence headquarters risked duplication and ambiguity in relation to the North Atlantic alliance and was to be discouraged by every possible means. Anything that might resemble a joint military force – or, heaven forbid, a real-live European army – was both ridiculed as impracticable and ruled out of order.

And for a long time, through the 1990s and early 2000s, this was Washington’s view, too. But it never quite convinced. On the one hand, the US wanted the European members of Nato to accept more of the expense and obligations of membership; on the other, it rejected outright any move to a coordinated EU defence that might help to do this. The British stood with the US.

Under President Obama, however, it seemed that Washington’s objections to EU defence coordination were softening. The calls for the European members of Nato to contribute more were as loud as ever. But the particular objections to the EU developing a defence arm were less often heard.

Indeed, as the East and Central Europeans worried about a resurgent Russia in the wake of its annexation of Crimea, there seemed to be something almost akin to acquiescence in Washington that the EU might be part of a solution. Suddenly, the UK risked being the odd country out.

Brexit, or its prospect, could leave the US and the EU on the same page. It could even open the way for a new, trilateral, area of cooperation. By leaving the EU, the UK takes a chunk of the budget with it, and an even bigger chunk of its defence capability. Part of the EU’s new security initiative may be about trying to plug that gap.

But it is also designed to respond to a new, and specifically EU, need, in the light of the migration crisis and its threat to the Schengen agreement. The inadequacies of EU security were highlighted in the summer of 2015 and the EU’s defences remain a botched job, haphazardly reinforced by restored border controls and fences at vulnerable points.

A strong argument could be made for a pan-European defence force to remedy this. Border control, however, remains a national, not EU, competence, and one that is jealously guarded especially by the “new” EU members. Extending the remit even of Frontex is controversial. Yet it is hard to see how else the demands can be met on the one hand for a more secure external border and on the other for continued free movement. The joint defence initiative now being broached is a start.

It is a start, though, and it could lead to what has been called a “two-speed” EU, with an inner core of states that accepts the whole package – a single currency, free movement and joint defence arrangements – and an outer group for whom this whole package is unacceptable, either in principle or practice, or both.

It is coincidence, but also telling, that the EU presidency should be held at such a time by Slovakia, a member (with Hungary, Poland and the Czech Republic) of the Visegrad group, which wants stronger defences and continued free movement but baulks at accepting a system of quotas for refugees on grounds of practicality and national sovereignty. Its biggest member, Poland, has also put its entry to the single currency on hold.

In essence, the very same contradictions and competing arguments that contributed to the UK’s departure can be seen at the other edge of Europe, too.