Stronger external security of liberal democracy is one thing that the UK is good for. The second is international peace, trust, and solidarity within the British Isles. We often forget, especially if we’re English, that the UK is a multinational state, comprising a union of English, Welsh, Scottish, and Irish peoples. Each of those peoples has maintained its own national customs and has either retained or acquired its own institutions. Within the UK, the Scots have always preserved their own law, established Church, and education system; the Welsh language flourishes far more strongly than the Irish language does in the Republic across the water; and Northern Ireland had its own legislative assembly long before either Wales or Scotland. So successful has our Union been that the thought of violent conflict erupting between its constituent peoples is almost unimaginable.

However, contrary to Alex Salmond’s glib reassurances that the “social union” between England and Scotland would survive Scottish independence, my own view is that a “Yes” vote last September would have kindled a degree of mutual hostility that these islands have not witnessed since the 18th century. The negotiation of separation would have been tough and fraught. The separating Scots would not have got all that they wanted, they would have been frustrated, and their traditional resentment of England would only have deepened. For their part the English, having woken up to the costs and risks of the dissolution of the UK, including the permanent weakening of Britain’s international prestige and power, would have discovered a general resentment of the Scots that they had never before had reason to feel.

Maybe the mutual alienation would only have lasted a generation or two, maybe no blood would have been shed — but maybe not. One of the nobler intentions of the Union was precisely to end recurrent warfare between Scotland and England, and it has been one of its finest achievements to make bloody conflict so unimaginable as to appear impossible. But appearances deceive here too: imagination is no constraint upon possibility. Anglo-Scottish peace (like European peace) is a fragile historical achievement — not a cosmic fixture. And as we know from the 30-year-long Troubles in Northern Ireland, which formally ended only in 1998, history can roll alarmingly backwards.

Peace, however, can be more than just the absence of violence; it can also be widespread trust and solidarity, and in Britain it has been. In this respect the United Kingdom already is what the European Union can only dream of becoming. In general, taxpayers in wealthy London do not complain when their taxes are used to support poorer people in Wales, Scotland, or Northern Ireland. That is because, in general, they identify with the Welsh, Scottish and Northern Irish, recognising them as their own people — as fellow-Britons. Compare that with the appalled reaction of most Germans to the prospect of having to bail out the crippled economies of Greece or Italy in the wake of the recent financial crisis. The contrast brings to the surface the extraordinarily high degree of international solidarity that we have achieved here in the UK.