British Prime Minister Boris Johnson makes eliminating the risk of terrorism sound simple. In the wake of last week’s knife attack near London Bridge at a conference on prison rehabilitation that killed two participants, he claimed ill-judged reforms instituted by the previous government were behind the early release of the assailant, a convicted Islamist terrorist. With a general election looming, it was inevitable that the tragedy would be seized on for political gain; he has ordered that 74 other cases be reviewed. But recovery of seriously radicalised people is a complex issue that cannot be resolved so easily, especially when there are serious shortfalls in funding. The 28-year-old killer, shot dead by police, had been released on appeal after serving half of a 16-year sentence for involvement in a plot to bomb bars, attack the London Stock Exchange and set up a jihadist training camp in Pakistan. Inspired by the al-Qaeda Islamist group, he was freed a year ago without his case having been reviewed by a parole board, as had been ordered by the sentencing judge who had determined him to be a serious risk to be set free only after proper assessment. He had never taken part in a rehabilitation programme and had passed himself off to prison authorities as repentant and reformed. His ploy was made easier in the British system, where underfunding means prisons are overcrowded and short-staffed and rehabilitation services lack resources. Even then, there is the question of how to detect whether a prisoner is genuinely reformed. Johnson’s order is necessary and sensible, but does not get to the root of the problem. Putting convicted terrorists behind bars indefinitely is no solution in most cases, nor is it feasible given constraints on resources; Britain has hundreds of such people. Southeast Asia has thousands in Indonesia, Malaysia and the Philippines and the numbers are likely to rise with nationals returning from fighting with Islamic State in the Middle East. Properly resourced rehabilitation is the accepted way to deradicalise extremists. But the latest London attack, by a jailed terrorist released early and armed with kitchen knives, highlights the complexities and challenges for governments.