Suggestions that Brexit could threaten the peace and stability of the UK, Europe and even the globe have not gone down well with the Leave campaign. Boris Johnson went so far as to ridicule the PM's "talk of World War III and bubonic plague" as "totally demented frankly". Yet in all the sarcasm, Brexiteers have no cogent response to what is increasingly being recognised as one of the most powerful warnings against a British exit from the European Union.
Be in absolutely no doubt - Brexit poses a grave threat to the very existence of the EU, which will inevitably threaten global stability with frightening and inescapable ramifications for the peace and calm of the United Kingdom.
With the Middle-East aflame, Russian aggression in its former domains, North Korean nuclear tests, etc, etc there could not be a more dangerous moment to challenge and potentially collapse a key institution of the post-WWII global political order, especially an EU built on the premise of saving Europe from the self-destructive tendencies that sparked centuries of conflict.
For despite all its failing - and of course there are some as otherwise there would not be a need for this referendum - the EU's role as an institutional buffer against a return to the horrors of world wars and the Holocaust is underestimated at our great peril.
Indeed, many have forgotten that it was a desire to avoid these wars, not economic or political union itself, that was the driving force behind the institution that today we call the EU.
In 1950, the then French Foreign Minister Robert Schuman proposed a Franco-German common market for coal and steel - vital commodities that had played such a role in previous conflicts between these European neighbours - to "make war not only unthinkable but materially impossible". The European Coal and Steel Community (ECSC) was born, later evolving into the EEC, then the EC, and finally the EU.
The underlying ethos of the ECSC was turning hyper-nationalist competition between great European empires into economic and thus political cooperation, in the hope that this would remove the centuries-old engine of conflict that culminated in two world wars exploding from Europe.
European nationalism had become a zero-sum game, with European states, enriched by their empires, viewing competition and outright military conflict with other European states as both inevitable and desirable. Conflict was celebrated across Europe (long before fascism's emergence) as a natural and positive expression of the progress of the nation.
And the UK was by no means immune. British officials across the empire in the years before WWI regularly referred with pride to the "Anglo-Saxon race", with HM's officials and politicians in Australia talking of their obligation to the "maintenance of the Mother-country's naval power, by which alone the unity and supremacy of our race as a whole can be guaranteed" (Letter from Bruce Smith to Andrew Fischer, 20 May 1909, on the state of Empire, Australia and Defence Papers of Andrew Fisher, NLA MS 2919, Item 2919/6/47).
Thus, until the political unity of the EU, European states at war almost inevitably means the United Kingdom and European states at war too - Napoleon, the Crimean War, the Great War, WWII, etc, etc.
In one fell swoop the project for European unity changed Europe's collective direction, removing its greatest driver of extreme nationalism and frequency wars, and redefined the global security environment in the process. As the former Taoiseach of Ireland John Bruton put it "The European Union is the world's most successful invention for advancing peace. Following two world wars that claimed over 75 million lives in a single generation, it was created to prevent deadly conflict from ever again engulfing Europe. Since the creation of the EU... Europe has enjoyed the longest period of peace in its history."
This was recognised in 2012 when the EU was awarded the Nobel Peace prize - while ridiculed by Eurosceptic elements of the British press at the time, the award reflected the global political awareness of what European unity has contributed to global peace and stability. The Nobel Committee recognised that, now more than ever, the stability the EU had achieved needed to be celebrated - "In this time of economic and social unrest... (the Committee) wished to reward the EU's successful struggle for peace, reconciliation and for democracy and human rights."
The EU is of course no panacea to global conflict - war, political violence and oppression remains commonplace across the world, and no version of European unity can ever cure this entirely. But the absence from the European Union of the conflicts so prevalent elsewhere is thus all the more remarkable, and yet is consistently taken for granted or ignored.
Europe of course faces huge challenges today - ongoing economic strain, terrorism and the migration crisis all play into the hands of the Far-Right and Far-Left - but look how different things are today from a very similar crisis in the late 1920s and early 1930s. European cooperation and unity, delivered through a variety of institutions built to protect democracy and stability in Europe, have helped ensure that more often than not rational political decision-making prevails.
How much more dangerous would the situation be now if the protectionism of the early 1930s - with each state pursuing their own interests irrespective of how others were harmed - had been the response to the financial crisis after 2008?
While it took too long for EU leaders and the Remain campaign to stress this vital issue, the merits of the argument have been further emphasised by the total absence of a cogent response from the Leave camp. Boris Johnson offers nothing but ridicule, and when I have challenged members of the Leave camp on the issue the response has been risible.
One senior Brexiteer I spoke with recently refused to accept that peace had anything to do with the foundation or development of what is now the EU, actually unaware of many basic facts, and when asked how he explains the unprecedented decades of peace in Europe all he could muster was that democracies don't go to war with other democracies. Reliance to such a lazy and evasive argument - that at best is a hugely debatable one - dramatically demonstrates that many in the Leave camp do not understand the lessons of history and what is at stake from a Brexit.
Voting in the referendum without considering the long-term peace and stability implications for the UK, Europe and the globe would be an act of remarkable shortsightedness.
For the choice we are faced with is crystal clear - continue to live with some loss of national sovereignty in return for the continuation of UK and European peaceful cooperation and unity, or choose the not-so-splendid isolation that comes with full sovereignty irrespective of how it might harm our peace and stability. Choose the latter and we will likely return to the divisive state-on-state rivalries that inexorably lead to continental and global conflicts.
As General Sir Mike Jackson - who led the UK's armed forces from 2003 to 2006 - has asserted, Brexit "could open a Pandora's Box", initiating a chain reaction of nationalism and instability in Europe.
Whether we like it or not, as Kofi Annan stated when UN Secretary-General, “More than ever before in human history, we share a common destiny. We can master it only if we face it together”. Those desperately clinging to the fallacy that the truth is otherwise - the Brexit advocates who celebrate the desire for Britain to 'go it alone' no matter the consequences - are myopic to our country's and continent's history, and are thus playing Russian roulette with the future stability of the nation.
Now that is what I call 'totally demented'.