Theresa May’s premiership has gone through many phases. It has also gone through many phrases. Mrs May is famously wedded to her unchanging verbal formulas. She subjects them to merciless repetition. They become extremely familiar. We may wish it otherwise, but few can forget such clunky classics as “Brexit means Brexit”, “strong and stable leadership” and “nothing has changed”. Last month, as negotiations on her EU deal reached a climax, Mrs May started to use a new phrase. The sheer novelty caught the attention. Until November, “the UK family” had not previously played a role in Mrs May’s speeches. Suddenly, the phrase was rarely absent from them.

What does “the UK family” actually mean? The immediate reason Mrs May started using it was to have a formula to cover not just the United Kingdom’s departure from the EU but the departure of other British possessions too. Prime among these was Gibraltar, the subject of a last-minute spat with Spain before the deal was struck. Britain’s “sovereign” military bases and installations in Cyprus were covered by the “UK family” too. So were the crown dependencies in the Channel Islands and the Isle of Man. “The UK family” is a pregnant phrase. Doubtless much thought went into it. There is no doubt that Mrs May intends it to imply that the UK, for all its differences and difficulties, possesses a shared life, a shared loyalty and a shared set of values that bind its individual parts together, just as an extended family is sometimes bound together. There is unquestionably, much truth in that.

Northern Ireland

Yet it is quite a stretch to apply these shared values and identities to Gibraltar, the Channel Islands and the Isle of Man. Most of these places, after all, are faraway places of which most British people know little. They are also serious tax havens where rich Britons hide their money. Many people live there and domicile their businesses there precisely in order to avoid being in the UK, not in order to be part of it. Gibraltar and the Cyprus bases are also territory carved from their hinterlands at different times by British imperial power. Most people in Britain wish these places no harm, but have little in common with any of them.

The UK is a unitary state. It is not a value system. It has a border, a currency, a government, security forces and a place at the international table. Yet it is not a traditional unitary state. It is also simultaneously a union of different countries and traditions. All of these retain highly distinctive features of their own, including, in some or all cases, legal entities, money, devolved governments and even, in some contexts, international recognition. Mrs May always insists on the primacy of the union, especially in the context of the Brexit vote. She has often talked, in the backstop debate, about “the integrity of the United Kingdom”. Yet these words and this approach suggest she is confused about what this union actually is. And she is not alone.

The starkest and most important example of this confusion concerns Ireland. Northern Ireland is part of the UK, but it is also, geographically and historically, part of Ireland too. It has a dual identity, not a sole, British, identity. It has much tradition, history, politics and law different from Britain, while also sharing much.

These differences cannot be wished away. They mean that it is simply ridiculous to pretend that Northern Ireland is in every respect the same as Britain. That is why the Northern Ireland issue has been so highly charged within the wider Brexit argument. These necessary differences around Brexit reflect Northern Ireland’s deeper distinctness from Britain. This ought not to be a controversial or provocative statement, if we understand what a union of this kind actually is. It is a union of different nations and traditions in which much is shared but where much remains distinct. The Democratic Unionist party’s idea that everything in the Brexit settlement – if there ever is one – has to reflect nothing except Northern Ireland’s place in the union is only true if we accept that difference is inherent to that union. The DUP does not accept that.

A complex union

Mrs May has been unreasonably indulgent to the DUP. She needs its votes in a hung parliament. But she is plain wrong to treat the DUP as the voice of Northern Ireland. It is the voice of part of it. Even then, its support of Brexit is at odds with the majority and with very large parts of its own electorate. It is therefore to Mrs May’s credit that she agreed with the EU to a backstop on Northern Ireland that did not and could not give the DUP exactly what it demanded. Those who oppose her backstop plan do not understand the UK union.

Mrs May often speaks of the union as beloved or precious. She is right to recognise that it is a remarkable construction. But, from the context of her comments, she appears to regard the union simply as the union with Northern Ireland. Yet this is only one part of the UK union, and it is not a typical one. As a result, Mrs May gives the impression of loving many of the wrong things about the union and not loving the things that deserve approval and support.

The UK is a complex union. In a democracy, people can be united by their differences. Mrs May’s failing, and the failing of many others in all political parties, is not to recognise that complexity. The union with Northern Ireland emerged from a treaty with Irish nationalists in the early 20th century. That with Scotland followed the union of the crowns and, later, the parliaments in the 17th and 18th. The union with Wales, if it can even be called that, was a 16th-century punishment after the Glyndŵr rising. Modern devolution has given significant powers back to each country, but on an uneven basis. England, meanwhile, has no self-government as such at any level. The union is not based on a heroic model but one that is anti-heroic.

Like a family

In that respect, and topically for Christmas, it is indeed a bit like a family. Families are not ideal, inflexibly hierarchical or indestructible. They are complicated and changing, held together by bonds of tradition and affection but not always seeing things in the same ways. The distant tax havens may be distant relations, but they are also family embarrassments. The relationship between the component parts of UK society can be that of a family which comes together for – and quite enjoys – family weddings and special occasions but in other respects leads largely separate lives. This isn’t at all what Theresa May meant by the phrase “the UK family”. Yet, without quite meaning it or understanding it, she may actually have got it right after all.