There had been talk among unionists of street parties to celebrate Brexit day. Flags and bunting and maybe even bonfires. A royal visitor. But it hasn’t turned out that way.

A woman I know lives on a housing estate in one of those small Northern Irish towns that doesn’t take its union jacks down after the summer marching season, so that by the end of winter, the wind and rain have whipped them into faded rags. She tells me that among her family, friends and neighbours, she thinks she is the only one who voted in 2016 to remain in the EU. “I knew the role the EU has had in peacebuilding here and I knew it allowed the inward investment of migration when Northern Irish people were leaving,” she says. “Westminster didn’t care about us and nor did the south. The EU did.” Why did the rest of her circle vote for Brexit, I ask her. “A border as high as you can get and all the foreigners out,” she says.

Instead they got what loyalists and many other unionists of a less staunch stripe, who had other reasons to support Brexit, are calling the betrayal act. In the interests of keeping a soft border with the Irish Republic, Northern Ireland is to remain in closer economic alignment to the EU than the rest of the UK, and is to be separated from what unionists think of as the mainland by what is being described as “a border in the Irish sea”.

The Brexit deal was unanimously rejected by the newly reinstated Stormont assembly last week. Boris Johnson doesn’t care. The glummest faces were those of the Democratic Unionist party, which had with such enthusiastic arrogance sold its votes to prop up the Tories at Westminster in exchange, it thought, for power and a hard Brexit. Now the DUP feels betrayed by the British, and loyalists feel betrayed by the DUP. There is no more talk of “our precious, precious union”. And there are moderate nationalist SDLP and cross-community Alliance MPs taking their seats in Westminster, so the DUP can no longer claim to be the voice of Northern Ireland.

Brexit has hastened the decline of the once dominant Ulster Unionist party (UUP), too. Steve Aiken, its new party leader, began the recent Westminster election campaign boldly declaring it was pro-remain and that it would stand in all of NI’s constituencies. Within days he had to retreat and the party returned no MPs.

‘The Alliance party’s leader, Naomi Long, has dispelled its old image as the ‘nice’ party for the essentially apolitical.’ Photograph: Michael Cooper/PA

Both the UUP and DUP lost votes to the Alliance party, which opposed Brexit. Its leader, Naomi Long, has dispelled its old image as the “nice” party for the essentially apolitical. It appeals to those young people for whom the constitutional issue is not a priority. As the new justice minister at Stormont, one of her first moves has been to seek to extend to Northern Ireland UK laws protecting women from domestic violence.

When the EU’s chief Brexit negotiator, Michel Barnier, visited Belfast earlier this week, he paid tribute to civic society in Northern Ireland. Both EU and UN bodies provided backing for the work of NGOs and activists who used the three years during which there was no executive at Stormont to build strategic partnerships based on human rights, and to bring in same-sex marriage and access to abortion. The DUP, which insists that Northern Ireland must be treated exactly the same as the rest of the UK, vehemently opposed this extension of rights that already existed for other British citizens. There already was an invisible border in the Irish Sea.

In 2014 it was a DUP minister who ended pay parity between nurses in Northern Ireland and colleagues elsewhere in the UK. The trade unions eventually won it back this winter with strikes that were massively supported by the public as a model of post-Troubles integration. Those involved included members from both of Northern Ireland’s main communities, as well as the many EU and other migrant workers whose right to remain post-Brexit may now be in jeopardy. Any loss would be felt in the teetering health services.

A century after the foundation of the Northern Irish state, unionism is demoralised. Brexit has backfired on them, and the English nationalists who drove it have not hidden their contempt for the most British of Britain’s subjects in this last fragment of the empire, now that they no longer need them. The parties in the north are in agreement that far less money has been provided from the Treasury than was promised in the deal that reopened the Stormont assembly and executive. The British secretary of state’s response was to retort rudely on Twitter that they’d better just get on with it.

Sinn Féin has seized on Brexit as a way to pave the route to a united Ireland. Most nationalists and a growing minority of unionists can see the attraction, given that this would mean a return to the EU. Loyalists are harking back to opposition to home rule in 1912. Let’s just do that whole damned century over again but with a different ending. OK? Hands up. Anyone?

• Susan McKay is an Irish writer and journalist: the sequel to her book Northern Protestants: An Unsettled People will be published this year