Varadkar acts as if Brexit, not terrorists, will be to blame for violence

This fear has been centre stage in the UK’s negotiating tactics. London has conceded almost everything to Ireland and the EU to prevent a hard border.

It has even vowed not to have CCTV at the frontier, despite a Queen’s University finding that only 10% of nationalists would support vandalising cameras. London has let a dissident republican mindset dictate its Brexit policy.

Last week it was reported that Britain might commit Northern Ireland to stay in the single market forever, as part of its determination to placate Dublin. Happily, there is reported to have been ministerial backlash against this.

The PSNI chief constable George Hamilton has warned about the security implications of a hard border. If there is a hard border, Mr Hamilton will have a duty to police it, as the RUC and army did during the Troubles. But no-one, almost no-one, wants a hard border.

However, to increase the pressure on this issue, the Taoiseach Leo Varadkar has related to EU leaders the story of an IRA bomb attack at a customs post in Newry in 1972. When the UK was resisting such terrorism, it got precious little help from the Irish. That is a point that UK diplomats should make to EU ones. The latter might then put pressure on Dublin not to be so slack if indeed the terrorists return to terror in a disgraceful bid to get their own way.