CEP Senior Advisor Ian Acheson quoted: "Ian Acheson, a former prison governor who carried out a government-commissioned review of Islamist extremism in jails, said he had raised security concerns with ministers. 'The HSU is supposed to be our most extreme custody, holding some of the most dangerous people in western Europe,' he told The Independent. 'The fact that such a ferocious attack on staff could happen here is a huge security failure that ought to be a shocking wake up call for ministers.'"