Twenty-three years of peace in Northern Ireland, after a sectarian war that lasted 30 years and killed 3,700 people, but nothing lasts forever. Every night for the past week there were violent mobs of youngsters in the streets of Belfast attacking each other, Protestant against Catholic. And it’s all Boris Johnson’s fault.

The British prime minister didn’t mention it at the time, but his successful campaign to free the United Kingdom from the evil clutches of the European Union (Brexit) was only Phase One of his master plan. Phase Two is his plan to free England from the evil clutches of the United Kingdom.

A narrow majority of the English voted to leave the EU in the 2016 referendum, but both Scotland and Northern Ireland voted strongly to remain. That gave Phase Two a head start, because Johnson and the Brexiters were effectively forcing both Northern Ireland and Scotland to choose between England and Europe. In both countries the answer may be ‘Europe.’

For Scotland, it’s a simple choice. As a nation of five million with no major historical traumas or enemies, the Scots would probably be welcome to rejoin the EU. If the Scottish National Party wins a majority in Scotland’s May election, SNP leader Nicola Sturgeon promises to hold a second independence referendum ‘in the first half of the next (Scottish) parliament.’

Scotland’s last independence referendum, in 2014, came out 55-45 in favour of staying in the UK, but it’s hard to say how a second one would play. Many Scots deeply resent being dragged out of the EU by the English – but many would also be unhappy about a hard border with England. Whatever happens, it would be an entirely peaceful process.

Not so for Northern Ireland.

‘Norn Iron,’ as the locals say it, was created exactly a century ago at the demand of the militant Protestant majority, while the rest of the island got its independence as the (mainly Catholic) Republic of Ireland. Northern Ireland has been a running sore ever since, with the Catholic minority in the North yearning always for reunion with the Republic.

The Irish Republican Army (IRA), the main vehicle for those yearnings, waged an armed struggle against the local Protestants and the British government for much of that time, but the last round of the ‘Troubles’ ended in 1998 with the Good Friday peace agreement. Unfortunately, Brexit and Johnson have undone that deal.

The Good Friday deal enforced power-sharing between Protestant and Catholic political parties in the North and the border became invisible, with no checks at the crossings. Catholics in the North could even claim citizenship in the Republic if they wished.

It worked because most people were sick of the endless murders, and because the deal removed some major irritants for the Catholics, including especially the ‘hard’ border – but above all because the higher Catholic birthrate would deliver a Catholic majority in the North eventually, at which time reunification could come by a peaceful vote.

Brexit upended all that. If the UK left the EU, then there had to be a hard border somewhere since the Republic wouldn’t dream of leaving.

Putting the new customs and immigration controls in the obvious place, between Northern Ireland and the Republic, would wreck the Good Friday agreement and probably start the IRA bombing and shooting again. So Johnson chose to sell out the Protestants instead, by putting the new border in the Irish Sea, between Britain and Northern Ireland.

That’s how he got a Brexit deal signed with the EU – but to postpone a revolt against that border by ‘Loyalists’ (Northern Irish Protestants), he simply lied and said it wouldn’t operate as a border. There would be no customs checks, no paperwork, nothing of that sort at all – and the poor mugs believed him. Now they have woken up to the truth.

For practical purposes Northern Ireland is still in the EU, with a customs border between it and the rest of the UK. The Loyalists feel abandoned – and this comes just as the Catholic population of Northern Ireland finally catches up with the Protestants.

So it’s the Loyalist militias who are re-starting the war in the streets now, attacking the Catholics in the hope of stopping a slide into the Republic. Quite a lot of people could die before it’s over, but the slide is probably now unstoppable. Johnson will certainly not die in a ditch to stop it.

Which leaves only Wales. It’s hard to imagine Wales leaving 750 years after the English conquered it, but Boris Johnson is a universal solvent. Plaid Cymru, the Welsh nationalist party, is promising an independence referendum by 2026 if it wins next month’s election. Clean sweep for Boris?