A Troubling Report

It was the worst atrocity of the Irish Troubles: three bombs exploding within 90 seconds during rush hour in Dublin in May 1974, killing 27 and maiming hundreds. Ninety minutes later, another bomb went off outside a pub in Monaghan, killing seven. No one was ever charged with the crimes. Last week a four-year judicial inquiry concluded that it was probable, though not proven, that the loyalist paramilitaries who planted the bombs had help from low-level members of the British security forces.

Justice Henry Barron, the report's author, tried to probe whether senior British intelligence figures were...