Until recently I was a committed remainer and wedded to the belief that the best way out of this Brexit mess for the EU was simply to try to ensure it didn’t happen. But the events of the past month illustrate why there is, rightly, a growing mood in Brussels for a completely different outcome: for the EU to prosper, Britain must leave.

The rationale is simple, Brexit is – either now or in the not-so-distant future – inevitable. That is because Britain continues to demand impossible conditions for its membership of the community-based, compromise-led, multinational organisation the modern EU represents. Even in trying to exit, Britain is still arguing about “red lines” of its own making. This approach would only amplify if it somehow ended up remaining a member.

Britain already enjoys a privileged position in the EU, much to the chagrin of many other member states. Opt-outs from the euro, the Schengen agreement on passport-free travel, the charter of fundamental rights and on any European legislation related to freedom, justice and security have all been negotiated by successive British prime ministers.

European diplomats are exasperated at how this situation is still portrayed in Britain as the creep of an EU super-state. The Luxembourg prime minister, Xavier Bettel, put it best when he said the British “were in with a lot of opt-outs, now they are out and want a lot of opt-ins”. This situation is untenable for the future cohesiveness of the EU; it slows decision making, makes the setting of meaningful objectives difficult to achieve and acts as a brake on meaningful reform.

From a historical and political economy perspective, Brexit is an inevitability. Since Margaret Thatcher’s famous Bruges speech of 1988, where she set out a vision of a Europe based on “willing cooperation between sovereign states”, Britain and the EU have been like a married couple living increasingly separate lives. And the fault here is shared. Britain – most noticeably under Labour from 1997 to 2010 – lived the myth that the UK could have its EU membership but stand aloof from its development. Brussels refused to acknowledge that all the real love had long since passed.

British attitudes towards the Irish border question are a good example of the UK misunderstanding the EU at a most fundamental level. The backstop, which is designed to prevent the reimposition of a hard border between Ireland and Northern Ireland, is neither about trapping the UK in a permanent arrangement nor seeking to break it up. The widespread British view of the backstop shows a deep distrust of EU institutions and their role in protecting the interests of member states and maintaining a level playing field.

Another example is Britain’s famous “rebate” from its budget contributions to the EU. Were Brexit somehow to be reversed, there would be no support among other member states for these rebates to continue. Although unreported in Britain, the current negotiations in Brussels for the next budgetary period (2021-27) are progressing at pace. The shortfall (€12bn-15bn) caused by Britain’s exit will be met with higher contributions from other member states. Much more money will be allocated to emerging priority areas such as border control, research and development and climate change.

Britain never understood that contributing to the EU’s budget is not a commercial transaction, it is about investing in peace, stability and growth right on your doorstep. The fact is, without Britain, the internal functioning of the EU, including agreeing what to spend money on, becomes easier.

But here lies the crux of the problem for Britain. The sovereignty-sharing, legalistic model of integration embodied by the EU only succeeds because member states see the bigger, sometimes almost incalculable, benefits of membership. Raging arguments over migration, Russia and populism may be a feature of European council summits in Brussels. The European commission might take Hungary or Poland to task over reforms which threaten democracy. But none of these debates question the wider integrity of the EU project.

Britain today – from the gleaming towers of the City of London to the rusting coalfields of the Welsh valleys – is a microcosm of the challenges facing all post-colonial powers. But while France and Germany see European integration as the mechanism to secure peace and maximise their global role, Britain’s failing relationship with the EU shows that it is still searching for the right expression of its place in the world.

The future remains to be written, but for Britain and Europe one solution is obvious: a no-blame divorce followed by respect and friendship. After all, families are complicated, friends with benefits less so.