CEP Senior Advisor Ian Acheson writes: "No one is talking about these clandestine arrivals who have melted into the background, traumatised, exploited, enslaved. Yet they will include tomorrow’s violent extremists who do or will pose a threat to national security. We have literally no idea where these people are or the level of threat they pose. We do know that failed asylum seekers who do make it into the system and somehow remain stuck there, sometimes for years, have committed terrorist acts that have stunned this country."