The tragic death of Lyra McKee shows our carelessness towards the fragility of the Good Friday Agreement

It is not a cheap point to link the upsurge in violence – partly – on Brexit. The possibility of a hard border on the island of Ireland is something that inflames passions that not enough people on the eastern side of the Irish Sea, especially a new generation of British Tory politicians, sufficiently understand

The death of a journalist on the streets of Derry at the hands, it seems, of the New IRA adds a particularly sad and poignant dimension to the latest outbreak of low-level terror on Northern Ireland (by the standards of the worst years of the Troubles).

Lyra McKee was doing her job, and it cost her life. It highlights the risks that brave reporters take in every war or conflict, including riots and demonstrations, and we know only too well that journalists are now actively targeted by some groups, and most barbarically by so-called Islamic State and by Syrian government forces.

The Police Service of Northern Ireland, who were the main targets of a gunman firing indiscriminately, say that McKee was not being targeted. In truth, however, the violence would be no less reprehensible and sinister were it a PSNI officer who was left dying in Creggan. A life is a life, whether in uniform or not.

It is dismal to see, like a replay of the bad old days, petrol bombs being lobbed at armoured police Land Rovers, the anger and hatred revived by yet another of the very many Irish loaded anniversaries – in this case the Easter Rising of 1916. Local elections seem to have stirred up resentments as well. With the Stormont power sharing executive in abeyance for more than two years now and no sign of reconciliation, the atmosphere was becoming combustible.

Like the recent amateurish Republican letter bombing campaign, these events serve as a reminder that dissident republican groups are growing more militant. It is not a cheap point to link the upsurge in violence – partly – on Brexit. The possibility of a hard border on the island of Ireland is something that inflames passions that not enough people on the eastern side of the Irish Sea, especially a new generation of British Tory politicians, sufficiently understand. When Boris Johnson talked about the Irish border issue as “the tail wagging the dog” in reference to Brexit he betrayed a terrible indifference to the lives of people in the province. When he fetched up at the Democratic Unionist conference to gather some support for himself and his ambition to be PM he showed he simply didn’t care about being seen to “take sides” in the historic divisions. Theresa May also displayed a shocking carelessness when she formed her loose partnership under the supply and confidence agreement with those she described as “friends and allies” of the Tories, and bunged them £1bn to keep her in power. Much good it has done her. Taking sides with Arlene Foster was a very stupid thing to do.

There is a reason why British politicians have kept their snouts out of Ireland for a long time. John Major’s government has it right when it declared it had “no selfish strategic and economic interest” in keeping Northern Ireland in the UK. He and Tony Blair, like Ted Heath, Harold Wilson and even Margaret Thatcher, were circumspect about taking sides, despite sometimes tough action against the terrorists. By the way, these are also examples Jeremy Corbyn should take heed of: too many unionists in Northern Ireland distrust him as an honest broker for an honest and fair peace.

It is now 21 years since the Good Friday Agreement was signed, and too many have come to take peace for granted. The threat of a full-on civil war in Ulster is perfectly real. The war that has been going on, with pauses, for about 400 years was not ended in the 1990s indefinitely. The process was and is just that – a process, not an event. The collapse of political democratic arrangements and Brexit have proved too much for the peace process. Trust has gone, and created a familiar vacuum.

Brexit doesn’t justify violence and shooting journalists dead – nothing does. Even if a hard border with customs controls were established, and even if that required police and army backup to deal with terrorism, none of that should prevent a democratic decision about Brexit. The New IRA does not hold a veto over parliament.

But it is a hard political fact that some violence would undoubtedly be unleashed with a hard border, and we cannot know where it will end. The hard Brexiteers have to be honest about that and face up to years more of British military commitment to an unwinnable war if that wish to stop the tail wagging the dog is to be made effective. These Tories, and some Labour figures such as Kate Hoey, should also reflect that in such a volatile situation a new border poll could lead to Irish unification, just in time for the independence centenary celebrations in 2022. Do not forget Northern Ireland voted Remain (56 per cent) in 2016, and that Sinn Fein and nationalism have probably never been running so strongly since partition.

A simple fact can now be briefly restated: Brexit is incompatible with peace in Ireland, and demonstrably so. It is something all should be aware of, and as we were not in the 2016 referendum.

The oddest thing about these sad developments is to listen to Sinn Fein condemning Republican terrorism. The ironies are painfully obvious, but no matter. Sinn Fein is saying the right things. It might also be a moment to recall the Real IRA’s bombing of BBC TV Centre in London in 2001, in retaliation for a Panorama documentary. Isis is not the only group to target journalists, or indeed care little about any human life. Pub bombings, assassinations of MPs, random sectarian killings, torture, Bloody Sunday, Warrington, Enniskillen... do we really want to go through all that again for a trade deal with Donald Trump?