Stephen Grey is a good writer with a reputation for doggedness. He goes where a story leads, even if it doesn't suit his preconceptions.
But his sources on Northern Ireland seem to be on the intelligence side. A certain amount of special pleading is possible.
It is plausible, but easy, to claim that agents simply didn't tell their handlers things that endangered them or their family and friends. They let some attacks through to preserve their lives or their cover.
This picture of people high on the adrenalin of spying, friends with their handlers but ultimately trapped in a relationship once they have begun, is fairly convincing. Agents who, like Martin McGartland, told handlers every detail tended to get caught when it was noticed that everything they were involved in went wrong.
Did handlers and managers try to preserve agents' cover by protecting them from prosecution when they committed crimes? We don't have evidence but official reports have not been ruling it out for years.
An important agent could make a police or Army officer's career. Winning his or her trust and keeping them in the field could be important motives to cover up, as Panorama recently alleged. Yet we cannot assume the worst in every case.
It is clear now that the spying operation was huge, involving some people who may now have a role in public life. Many are concealing an intelligence history as well as a paramilitary past. Learning the truth, just like the truth about who planned and executed terrorist attacks, would be a huge strain and it would need to be carefully handled.
We need to know our history, but we need to prepare for shocks.