Friday’s decision to drop murder charges against a member of the Parachute Regiment for his role on Bloody Sunday tells us that, even after 50 years, the rulers of Britain remain fearful of the full facts tumbling out.

Soldier F was a member of the death squad that went in with guns blazing as thousands milled around on Rossville Street in the Bogside area of Derry at the end of a 10,000-strong anti-internment march on 30 January 1972. In the space of 20 minutes, 13 unarmed men fell dead. Fifteen others were wounded. One of the wounded was to die from his injuries some months later.

The last thing the top brass and their political partners want is to see F, or any other member of the First Battalion of the Parachute Regiment, under cross-examination in public about what he did on the day and who gave him the go-ahead to do it.

It’s not that the upper echelons of the military or their political associates will be particularly concerned about the possibility of F being consigned to a cell for the rest of his days. He was a low-rank foot soldier, easily disposable.

What makes the officer class squirm has to do with what made Bloody Sunday different. The slaughter in the Bogside contradicts the standard narrative of the Troubles promoted not only by the British authorities but also by the mainstream media of both Britain and Ireland.

Almost all the atrocities that pockmark our past can be ascribed to people purporting to represent one community inflicting pain on the other community. But Bloody Sunday wasn’t like that, wasn’t planned or perpetrated by anybody from any side in Northern Ireland.

The men who brought a death-storm to the Bogside were uniformed to represent the British state.

Nowhere in the thousands of political and military documents released to the 12-year inquiry under Lord Saville can evidence be found of any local politician or political entity being consulted or informed in advance of paratroopers being drafted into Derry to police the civil rights parade, much less what they planned to do when they reached Rossville Street.

A number of Unionist figures responded to the killings at the time with a shrug of unconcern, even in some instances with unrestrained glee. They should have been smothered in shame back then. Their successors should be striving now to summon up a half-ounce of contrition.

But being a para means never having to say sorry, even for mass murder. It’s what they do, what they are trained and deployed to do.

The other key difference between Bloody Sunday and other atrocities is that Bloody Sunday happened in broad daylight and was witnessed, in many cases at very close quarters, by marchers crouched behind walls or huddled into local houses. They watched as fellow marchers were gunned down in front of them.

Nobody in the Bogside was waiting for an inquiry or a trial to tell them the truth. They were waiting to discover whether the truth would be told.

Bloody Sunday was out of the ordinary, but it wasn’t an isolated occurrence.

In August 1971, the same squad of paras had shot ten unarmed people dead over three days in Ballymurphy in west Belfast. There wasn’t even a pretend investigation.

The fact the squad had gotten away – or think that they have – with the massacre in Ballymurphy will have emboldened them in Derry. The fact that they’d gotten away with it – or thought that they had – in Derry will have given them a swagger of invulnerability when they found themselves on the Protestant Shankill Road in north Belfast the following September, where they shot Robert Johnston and Richard McKinney dead, innocent men walking in their own streets, posing no threat to anyone.

That’s one thing we can say for the paras – they are not sectarian; they’d kill anybody. And the British state will stand behind them.

The Bloody Sunday families intend to take judicial review proceedings in an effort to have the charges against F reinstated. It is right, of course, that every avenue should be pursued. But, at this stage, the chances of the paras being brought to book by the State are as near to nil as makes no difference.

The political conclusions to be drawn are profound.