This year marks the centenary of the foundation of Northern Ireland in 1921. It would probably come as something of a surprise to some of its architects, if they returned to Earth today, to learn that it lasted this long.

Ministers have reportedly set aside £3 million of public money to mark the occasion, although this probably feels like very small beer to Unionists staring down the barrel of the Northern Irish Protocol and the threat of economic partition from the mainland.

Of course, this danger might be overstated. In his summary of implications for Northern Ireland as part of our ‘The Deal in Detail’ series, Dr Graham Gudgin concluded that “the Union is safe enough”, and “nor are the costs of victory likely to be heavy, even if nationalists will of course strive to make them seem so”. He also believes that the impact of the Irish Sea border on day-to-day life will be light.

There are also grounds to be wary of a heads-we-win, tails-you-lose narrative peddled by some commentators in which a ‘united Ireland’ is brought closer by every option, be it a land border outraging nationalists or a sea one demoralising unionists.

However, it may be too early for so cheery an assessment. We are already seeing delivery services change their approach to Northern Ireland. Michael Gove wriggled away from pointed questions in Parliament about whether the ‘grace periods’ for things like foodstuffs are intended to buy time to negotiate arrangements which protect existing East-West links, or to give Ulster businesses time to set up new supply lines with the Republic.

Nor – as any Brexiteer should know – are the EU’s arrangements static. The Single Market regulations will be continually expanding, and as they do the areas of possible divergence between Northern Ireland and Great Britain will likewise grow. As the Province is not represented in EU institutions, this risks enhancing the prestige of Irish representatives who will try to take on that role – just as Dublin has already stepped up to fund both the European Health Insurance Card and places on the Erasmus scheme for Northern Irish residents.

In contrast with this assertiveness, historically Westminster has been extremely wary of doing much of anything which emphasises Northern Ireland’s place in the United Kingdom, even be it so innocuous as putting the Union Flag on its (British) driving licences. For their part, the non-integrationist majority of local Unionists have been reluctant to fully engage with mainland politics for the fear – far from ungrounded, as Boris Johnson’s u-turn on the Protocol illustrates – that they have few real allies there.

The upshot of this is the vicious cycle of devolutionary unionism at its most advanced, perhaps morbid stage, which amounts to substantial cash transfers between parts of the country with increasingly little institutional or social integration to justify it.

With Brexit now ‘done’, to a given value of done, it looks as if the Union is shaping up to be the central plot of Season 2 of the Johnson premiership. The main focus is inevitably on Scotland, and the looming showdown which beckons after they likely secure another separatist majority in the Scottish Parliament in May. But the Prime Minister has bridges to build (perhaps literally) with Northern Ireland too.

He should start by appointing a Northern Irish Secretary – probably from the Lords – with a deep pre-existing interest in the Province, and task them and their special advisers with finally articulating a proper case for the British Government as to what its obligations under the Belfast Agreement actually are. The past few years have been a painful exhibition of how Dublin has effectively memed their London counterparts into accepting an absurdly maximalist interpretation of those obligations by providing incurious politicians with easy homilies.

Beyond that, the Province needs to be included in the same mission the Government has set itself for Scotland: reviving Westminster as a positive and pro-active force in every part of the kingdom. If Dublin is sponsoring the Erasmus scheme, which as Tom McTague puts it “builds a sense of Europeanness”, Ministers should respond not just with the global-facing Turing initiative but the mooted Home Nations alternative to encourage cross-border mixing amongst the next generation. British investment in key infrastructure, be it the M4 Relief Road or a ‘floating tunnel’ to Northern Ireland, should also be seriously considered.

The Conservatives can’t save the Union on their own, and Labour’s refusal to let go of their idée fixe – endlessly passing power away from the centre in the hope that at some point the problem goes away – remains a pressing problem. But the best way to try to shake them out of this orthodoxy would be to demonstrate that the alternative can work.

If the Prime Minister wishes to keep Northern Ireland inside the UK, let alone perhaps see it one day exercise its democratic right to set the Protocol aside and reintegrate with Great Britain, he needs to make the Union a compelling proposition. If he truly sees himself as “the greatest unionist that has ever occupied Downing Street“, it’s time to prove it.