The jailing of Royal Marine Ciarán Maxwell for terror offences raises troubling questions for the military.
How was an Irish republican with links to violent dissidents able to infiltrate an elite Royal Navy unit and evade detection for so long?
For five years, Maxwell researched, acquired and stockpiled an arsenal of weapons, including material stolen from his base.
A former Army officer has called for an overhaul of the vetting system.
On the face of it, when the man from Larne, a coastal town in County Antrim, began the grueling 32-week training to become a Royal Marine in 2010 he could not have seemed prouder.
Read the whole story from the BBC.
Featured image courtesy of the Metropolitan Police